file no.3-0520 · file no. 3-0520 national transportation safety board washington, d. c. 20591...

File NO.3-0520

AIRCRAFT ACCIDENT REPORT Continental Airlines

Saberliner Model NA-265-60, N743R Montrose, Colorado

April 13, 1973

Adopted: November 7 , 1973

NATIONAL TRANSPORTATION SAFETY BOARD Washington, D.C. 20591

/ / Report Number: NTSB-AAR-73-19 I

TECHNICAL REPORT STANDARD TITLE PAGE . Report No. 1 2.Government Accession No. I 3.Recipient's Catalog No. ITSBiAAR-73-19 I . Title and Subtitle .itcraft Accident Report - Continental Airlines, 5.Report Date

iabreliner Model NA-265-60, N743R, Montrose, Colorado, 6.Performing organization

8.Performing Organization

November 7, 1973

1973 Code

Report No.

. Performing Organization Name and Address 10.Work Unit No. National Transportation Safety Board Bureau of Aviation Safety

1184 11.Contract or Grant No.

Washington, D. C . 20591 13.Type of Report and Period Covered

Aircraft Accident Report 2.Sponsoring Agency Name and Address April 13, 1973

NATIONAL TRANSPORTATION SAFETY BOARD Washington, D. C. 20591 ' 14.Sponsoring Agency Code

5.Supplementary Notes

This report contains Aviation Safety Recommendations A-73-107 & 108.

after takeoff from Montrose Airport, Montrose, Colorado, at 1635 m.s.t., on April13 A Continental Airlines Sabreliner, Model NA-265-60, N743R, crashed shortly

1973. The two pilots were killed, and the aircraft was destroyed by impact and fire

Witnesses saw the aircraft climb straight off the runway to about 1,000 feet above the ground, make a shallow right turn, and then begin a left turn which steepened as the nose dropped. After the crash, an examination of the left engine revealed that the left engine thrust reverser was in the deployed position.

this accident was the continued operation of the left engine at climb power after The National Transportation Safety Board determines that the probable cause of

an unwanted in-flight deployment of the left engine thrust reverser, which resulted in a deterioration of aircraft performance.

Two reconnnendations were made to the Federal Aviation Administration.

17. Key Words

Thrust Reverser System, Full Climb Power

18.Distribution Statement This document is available

National Technical Inform-

Virginia 22151

to the public through the

tion Service, Springfield,

19.Security Classification 2Z.Price 21.No. of Pages 20.Security Classification (of this report) (of this page)

UNCLASSIFIED 23 UNCLASSIF IED NTSB Form 1765.2 (11/70)

ii

1 . 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 1.14 1.15 1.15.1 1.16 1.16.1 1.16.2 1.16.3 1.16.4 1.16.5

1.16.7 1.16.6

2 . 2.1 2.2

3 .

TABLE OF CONTENTS

I

Synopsis . . . . . . . . . . . . . . . . . . . Investigation . . . . . . . . . . . . . . . . .

Damage to Aircraft Injuries to Persons

0 ther Damage . . . . . . . . . . . . . . . . . Crew Information . . . . . . . . . . . . . . . Aircraft Information . . . . . . . . . . . . . Meteorological Information . . . . . . . . . . Aids to Navigation . . . . . . . . . . . . . . Aerodrome and Ground Facilities Comnications

Flight Recorders . . . . . . . . . . . . . . . Fire . . . . . . . . . . . . . . . . . . . . . Tests and Research Survival Aspects

Operational Tests of Thrust Reverser . . . . . Other Pertinent Information . . . . . . . . . . Thrust Reverser Operation . . . . . . . . . . . Thrust Reverser Advisory Lights . . . . . . . .

History of Flight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . Aircraft Wreckage . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . Thrust Reverser Lever Stop Assembly Thrust Reverser Control Switch

Previous Incidents of Unwanted Thrust Reverser

Operational Information Deployment in Flight

Analysis and Conclusions . . . . . . . . . . . Analysis . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . (a) Findings . . . . . . . . . . . . . . . . . (b) Probable Cause . . . . . . . . . . . . . . Recommendations and Corrective Action . .# . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Thrust Reverser Emergency Stow Procedure . . .

. . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

1 1 1 2 2 2 2 3 3 3 3

4 3

4 5 5 5 6 7 7 8 8 9

. . . . . . . . . . . . . . . . . . . . .

11 9

12

12 12

15 15 16 16

Appendix A . Investigation and Heari . . . . . . . Appendix .. Aircraft Informatiod.' . . . . . . . . . Appendix .. Crew Information . . . 2 . . . . . . . .

iii

20 19

21

F i l e No. 3-0520

NATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D. C . 20591

AIRCRAFT ACCIDENT REPORT

id: November 7 , 1973

CONTINENTAL AIRLINES SABERLINER MDDEL NA-265-60, N743R WNTROSE, COLORADO

APRIL 13, 1973

SYNOPSIS

A Sabrel iner , Model NA-265-60, N743R, owned and operated by Contin-

Montrose, Colorado, a t 1635 mountain standard time on Apr i l 13, 1973. e n t a l A i r l i n e s , crashed shor t ly a f t e r takeoff from Montrose Ai rpor t ,

The two p i l o t s , the only persons on board, were k i l l e d and t h e a i r c r a f t was destroyed by impact and f i r e .

rado. Witnesses reported seeing t h e a i r c r a f t climb s t r a i g h t ahead a f t e r The a i r c r a f t was on a rou t ine f l i g h t from Montrose t o Denver, Colo-

takeoff t o about 1,000 f e e t above ground level , where i t s t a r t e d f i r s t a shallow r i g h t tu rn and then a l e f t t u r n , which steepened as the nose dropped. The aircraft crashed i n a 550 left-bank and loo nosedown a t t i -

reverser was i n the deployed posi t ion. tude. Examination of the wreckage disclosed t h a t t h e l e f t engine th rus t

\

The National Transportat ion Safety Board determines that t h e prob- ab le cause of t h i s accident was the continued operation of t h e l e f t engine a t climb power a f t e r an unwanted i n- f l i g h t deployment of t h e l e f t engine t h r u s t reverser, which resu l ted i n a de t e r i o r a t i on of a i r - c r a f t performance. As a r e s u l t of the inves t iga t ion of t h i s accident ,

Federal Aviation Administration. the Safety Board has made recommendations t o the Administrator of the

I . INVESTIGATION

1.1 History of F l igh t

Model NA-265-60, departed from Los Angeles In te rna t iona l Airpor t , Cali- On Apr i l 13, 1973, N743R, A Rockwell In te rna t iona l Sabrel iner ,

fo rn ia , f o r Montrose, Colorado, about 1345, L/ wi th th ree passengers and two crewmembers aboard. The f l i g h t t o Montrose was rou t ine ; however, according t o the passengers, who had ridden i n N743R many times, the landing a t Montrose was made f a r t h e r down the runway and with heavier

- 1/ A l l times shown herein a r e mountain standard, based on t h e 24-hour clock, unless otherwise noted.

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reversing than usual. The a i r c r a f t then taxied off the runway t o the r i g h t , onto a taxiway located about 1,900 f e e t from the end of the runway; i t then taxied t o a pos i t ion i n f ron t of the terminal building. The a i r c r a f t landed a t 1609 and was parked a t 1611.

About 20 minutes a f t e r they deplaned, the crew again boarded the air- c r a f t , s t a r t ed the engines, and taxied t o Runway 30 f o r a f l i g h t t o Denver, Colorado. The takeoff was made about 1633, opposite t o the d i r ec t ion of the preceding landing. The f u e l load was estimated, a f t e r

c r a f t gross takeoff weight was 15,500 pounds. the accident , t o have been 4,000 pounds of J e t 1-A f u e l , and the a i r -

No servicing was required while the a i r c r a f t was a t Montrose.

Five witnesses who had observed the takeoff and i n i t i a l climb described the takeoff a s normal. I n the opinion of two other witnesses , the takeoff r o l l was longer and the climb angle more shallow. According t o the witnesses , the a i r c r a f t a f t e r takeoff continued on the runway heading fo r about one-half mile and then s t a r t ed a shallcw bank t o the r i g h t . After turning r i g h t approximte ly 30° and reaching a height of approximately 800 t o 1,000 f e e t above the runway, the a i r c r a f t s t a r t e d t o bank

u n t i l i t s t ruck the ground. Some witnesses reported tha t the bank angle l e f t . A t t ha t point i t began t o lose a l t i t u d e , and continued t o do so

witnesses reported tha t the l e f t wing suddenly dropped when the a i r c r a f t and nosedown a t t i t u d e continued t o steepen a s a l t i t u d e was l o s t . Other

was about 200 f e e t above the ground.

The accident occurred i n dayl ight . The sun was 25O above the horizon on an azimuth of 215'. The a i r p o r t e levat ion is 5,759 f e e t .

1.2 I n j u r i e s t o Persons

I n j u r i e s C r e w Passengers 0 thers - Fa ta l 2 Nonfatal 0 None 0

0 0 0

0 0

1.3 Damage t o Ai rc ra f t

The a i r c r a f t was destroyed by impact with the ground and postcrash f i r e . The wreckage covered an area 400 f e e t long on a heading of 078' magnetic.

1.4 Other Damage

None.

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1.5 C r e w Information

Both p i l o t s received ground school i n s t ruc t ion and f l i g h t t ra in ing i n the Sabreliner a t the company p i l o t t ra in ing f a c i l i t i e s . (See Appendix B for de t a i l s . )

1.6 Ai rc ra f t Information

The p i l o t s were c e r t i f i c a t e d i n accordance with ex i s t i ng regulat ions.

owned and operated by Continental Ai r l ines . It was c e r t i f i c a t e d and maintained i n accordance with ex is t ing regulat ions . A t t akeof f , the gross weight and center of gravi ty were within prescribed limits.

N743R, a Rockwell In te rna t iona l Sabrel iner , Model NA-265-60, was

The engine reversers were manufactured by Rohr Indus t r i e s , Inc. The l e f t engine reverser was overhauled and i n s t a l l e d on January 25, 1971, and operated 732 hours thereaf te r . The r i g h t reverser was in-

a f t e r . The l a s t annual inspect ion on the reversers was accomplished on s t a l l e d a f t e r overhaul on March 19, 1971, and operated 703 hours there-

September 20, 1972. The l a s t t h rus t reverser r igging inspect ion was performed on December 12 , 1969, a s a r e s u l t of Rockwell Service Bu l l e t i n 69-29 (AD 70-209). No th rus t reverser r igg ing inspect ion was performed thereaf te r . (See Appendix C for addi t iona l a i r c r a f t information.)

1.7 Meteorological Information

The o f f i c i a l surface weather observations taken a t the Montrose A i r - p o r t fo r the times indicated were:

1540 - estimated 5,000 f ee t broken clouds, v i s i b i l i t y 40 miles , temperature 68' F., dew point 24O, wind from 240' a t 14 knots , a l t imeter s e t t i n g 29.90.

1650 - estimated 5,500 f e e t broken clouds, v i s i b i l i t y 40 miles, temperature 68' F., dew point 20°, wind from 240 a t 10 knots, a l t ime te r s e t t i n g 29.88.

1.8 Aids t o Navigation

No a ids t o navigation were involved.

1.9 Communications

There were no knavn d i f f i c u l t i e s wi th communications.

1.10 Aerodrome and Ground F a c i l i t i e s

of bituminous mater ia l . The runway threshold i s displaced 1,000 f e e t a t Runway 12/30 i s 7,000 f e e t long by 100 f e e t wide and i s constructed

the southeast end. During the landing and subsequent takeoff , work on a 1,500-foot extension a t the northwest end of t h e runway was i n prog-

way was displaced 889 f e e t from the northwest end. Movement of dump ress. To allow fo r the construct ion a c t i v i t y , the threshold of the run-

trucks over the dry, dusty s o i l adjacent t o the construct ion caused l a rge clouds of dust t o be blown by a westerly wind across t h e runway.

foot wide d i r t s t r i p crossed the runway a t a nearly 90° angle. This s t r i p extends about 1,000 f e e t t o the west s i d e of t h e runway and about 1,500 f e e t t o the east s ide .

Approximately 3,000 f e e t from t h e southeast end of Runway 30, a 100-

A t the time N743R took off from Runway 30, l a rge chunks of hardened mud were lying across the runway i n l i n e with the d i r t s t r i p . The inves t iga t ion disclosed t h a t the a i r p o r t manager had scraped t h e s t r i p , using a road grader with dual t i re wheels which picked up l a rge amounts of d i r t between the tires. A s t h e grader crossed the hard runway surface , clumps of hardened d i r t f e l l from the tires onto the runway.

A set of four high-tension electrical wires, oriented nor th and

Large f lorescent orange painted b a l l s were at tached t o t h e wires t o south, was located approximately 6,500 f e e t from the end of Runway 30.

alert p i l o t s t o t h e i r presence, since t h e wires lay across the approach path t o Runway 1 2 . The wreckage area was located about 1,200 f e e t t o the northwest of the wires.

1.11 Fl igh t Recorders

F l igh t recorders were not i n s t a l l e d i n t h i s a i r c r a f t , nor were they required.

1.12 Ai rc ra f t Wreckage

ponents and a l l con t ro l surfaces were accounted f o r i n t h e wreckage. A l l systems were examined, and there was no evidence of malfunction. The landing gear and speed brake were found i n the r e t r ac ted pos i t ion . The wing f l a p s were found i n the " f u l l d m " pos i t ion .

There was no evidence of i n- f l i g h t f i r e . A l l major s t r u c t u r a l com-

The No. 1 engine thrus t reverser was found deployed i n the reverse t h r u s t pos i t ion . The No. 2 engine th rus t reverser was stowed i n the

piece of aluminum f o i l was found wrapped around the leading edge of an forward th rus t pos i t ion . Powdery dus t was found i n both engines. A

i n l e t guide vane on the No. 1 engine. Aluminum s p l a t t e r was found on the a f t s i d e of the rearmost turbine blades of the No. 2 engine.

The engines were completely disassembled and examined a t the Con- t i n e n t a l A i r l ines f a c i l i t i e s i n Los Angeles. The compressor sec t ions of

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both engines sustained minor impact and r o t a t i o n a l contact damage. The combustion sect ions sustained loca l impact damage on the combustion chamber outer cases and t h e adjacent area of t h e combustion chambers. Alumi-

2 engine.

I i ~ num deposi ts were fused t o the domes of the combustion chamber i n the No.

The turbine case of the No. 1 engine sustained a complete circum- f e r e n t i a l f rac tu re . The second-stage turbine vanes were f r e e of t h e i r re ta ining pins and had sustained minor r o t a t i o n a l damage. Four blades were buckled. The turbine sec t ion of the No. 2 engine sustained minor r o t a t i o n a l contact damage. The turbine blades were sp la t t e red wi th fused aluminum deposi ts . The turbine s h a f t s of both engines were undamaged but were coated with o i l .

The Nos. 1, 2 , and 3 bearings of both engines were i n t a c t and f r e e

e i t h e r engine. Fuel was found throughout the f u e l systems of both t o r o t a t e . No metallic deposi ts were found i n the main o i l screen of

damaged . engines. Both f u e l controls were i n t e r n a l l y i n t a c t and r e l a t i v e l y un-

, The No. 1 engine t h r u s t reverser and i t s e l e c t r i c a l and hydraulic components were bench tested. No malfunction was found.

a i r c r a f t cockpit and cabin area. The Montrose F i r e Department equipment A fuel- fed f i r e broke out a f t e r impact and consumed most of the

with foam and water. arrived a t the scene shor t ly a f t e r the crash and extinguished t h e f i r e

1.14 Survival Aspects

This was a nonsurvivable accident.

1.15 Tests and Research

Rockwell In te rna t iona l furnished the following information regard- ing the p o s s i b i l i t y of fore ign object ingest ion by the engines i n forward or reverse- thrust modes:

"The engine i n l e t loca t ion above the wing t r a i l i n g edge sh ie lds

The use of chine nose wheel tires (mandatory on the Ser ies 60, i t from any object l iqu id o r so l id thrown up by the main gear.

pass beneath the wing and thus avoid the engine i n l e t . There is opt ional on Series 40) f l a t t e n s t h e nose gear spray pa t t e rn t o

no h i s t o r y of any problem with so l id objects thrown up by the nose gear. In t h e reverse th rus t mode, the lower exhaust gas plume directed downward and forward w i l l sweep the runway and kick up loose objects o r water spray. With cor rec t usage of the reverser

- 6 -

i n which reverse th rus t i s terminated at approximately 60 knots , the rearward r e l a t i v e wind created by the a i r c r a f t ' s forward speed keeps the engine i n l e t ahead of any mater ia l tossed up by the reverser gases. Reverser use i n t o lower than recornended speeds results i n exhaust gas ingest ion and presumably could lead t o foreign object ingestion."

1.15.1 Operational Tests of Thrust Reverser

In te rna t iona l Model 60 Sabreliner. The f i r s t t e s t was flown by a Rock- wel l In te rna t iona l engineering f l i g h t t e s t crew to determine the e f f e c t of reverse th rus t when the a i r c r a f t was i n a climb configurat ion and a t t i t u d e . After the f l i g h t , the chief t e s t p i l o t reported tha t with f u l l reverse th rus t on the l e f t engine and f u l l forward th rus t on the r i g h t engine, there was s u f f i c i e n t l a t e r a l con t ro l , with the use of a i l e - rons and rudder, t o bank the a i r c r a f t a s much a s 30' i n e i t h e r d i r ec t ion ;

produced very not iceable buffet ing which resu l ted i n cont ro l wheel move- however, a l t i t u d e and airspeed cquld not be maintained. Reverse th rus t

ment, but not i n movement of the instrument panel t o the extent t ha t the instruments could not be read. The reverser could not be stowed while

approximately 85 percent , or l e s s , the reverser d i d stow. the engine was a t f u l l power; however, when the power was retarded t o

After the accident , two f l i g h t t e s t s were conducted with a Rockwell

The second f l i g h t t e s t , made with a Safety Board inves t iga tor on board, e s s e n t i a l l y duplicated the f i rs t t e s t , with s imi la r r e s u l t s . The second t e s t s were conducted with the a i r c r a f t i n a climbing a t t i t u d e , landing gear and f l aps up, and a t an airspeed of approximately 160 knots.

gine power lever i n i d l e , deploying the reverser , and immediately there- Instantaneous reverser deployment was simulated by placing the l e f t en-

mately 90 perceht r/min). Balanced f l i g h t was maintained by manual input a f t e r increasing the engine th rus t t o match the r i g h t engine (approxi-

to the f l i g h t cont ro ls . From t h i s s t ab i l i zed configurat ion, the f l i g h t cont ro ls were released and the a i r c r a f t was allowed t o devia te from level f l i g h t .

lowed by an increased bank and heading change t o the l e f t . It was noted

knots wi th the l e f t engine reverser deployed and 90 percent r/min on each tha t while the a i r c r a f t was maintaining an indicated airspeed of 160

engine, i t s rate of descent was 600 f e e t per minute. Also, no con t ro l problems were noted i n any configurat ion of reverse ( f laps up o r down) a t indicated ai rspeeds ranging from 210 knots down t o s t ickshaker ac t iva- t ion speed.

The first a t t i t u d e change was a slow pitchup, approximately 2 O , fol-

stowed while the a i r c r a f t was tax i ing . Before the reverser reached the f u l l y stowed pos i t ion , however, the th rus t reverser cont ro l switch (located i n the cockpit on the engine switch panel) was placed i n the

After these t e s t s , the l e f t reverser was a l t e r n a t e l y deployed and

OFF PC short advisc s h i e t deplo: three

not 1 slaw1 the x powel

peak, enou chec retu

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1.11

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- 7 -

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IPU t I t

OFF pos i t ion , which shut d m the system, placed the reverser doors j u s t

advisory red l i g h t (located i n the cockpit i n the center of the eyebrow shor t of the locked pos i t ion , and il luminated the l e f t reverser unlock

deployed when the power was a t 75 percent. The procedure was repeated sh ie ld ) . Power was then applied t o the l e f t engine, and the reverser

three times with the same r e s u l t .

not locked, the reverser doors would deploy i f f u l l power was applied slowly. Rapid appl ica t ion of power, on the other hand, had no e f f e c t on the reverser posi t ion. The e f f e c t of prolonged operat ion a t the high- power setting was not determined during the test.

Subsequent testing revealed t h a t when the reverser was stowed, but

Further tests conducted with the Model 60 Sabrel iner indicated t h a t peak-pressure values i n the hydraulic system r e t u r n l i n e s were not high enough to re lease the primary th rus t reverser locking mechanism should the check valve malfunction i n the th rus t reverser hydraulic con t ro l valve r e tu rn l ine .

1.16 Other Pert inent Information

1.16.1 Thrust Reverser Operation

I

which, when deployed, direct engine exhaust gases forward over and under The reverser assembly cons i s t s of two v e r t i c a l l y oriented doors

the engine nacel le . I n the stowed pos i t ion , these doors form the a f t sec t ion of the engine nacel le f a i r i n g . They are e i t h e r deployed or stowed by a hydraulic ac tua tor through a s ing le pivot system. The a c t u a t o r , located on the outboard s i d e of each reverser, i s connected t o two main drive l inks which, i n turn , a r e attached t o separa te d r i v e fittings on each door. The ac tua tor incorporates an i n t e r n a l lock which provides the primary means for r e t a i n i n g the reverser i n the stowed pos i t ion . Secondary locks, actuated by a latch lock solenoid, are provided f o r the doors i f the ac tua tor lock should f a i l . Appropriate electrical advisory indica t ing switches are incorporated t o denote t h e condit ion of the reverser doors.

ca t ion , and reverser door stowing i s made by a th rus t reverser cont ro l lever i n the cockpit . This cont ro l lever , which i s mounted on the engine thrus t cont ro l lever ( t h r o t t l e ) , i s normally positioned forward and below the t h r o t t l e lever knob. When the t h r o t t l e lever i s a t IDLE, and the reverse thrus t cont ro l lever i s pulled up and a f t , the reverser doors deploy. Once deployment of the doors is i n i t i a t e d , appl ica t ion of reverse thrust (engine th rus t increase) i s r e s t r i c t e d by a solenoid in te r lock i n

position. The reverser con t ro l lever can then be moved a f t to increase the reverser cont ro l lever system u n t i l t he doors reach the f u l l y deployed

engine th rus t for maximum reverse th rus t . Reverse th rus t operat ion is

Select ion of reverser door deployment, reverse th rus t power appl i -

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terminated by moving the cont ro l lever forward and down, thereby reducing engine th rus t and staving the reverser doors. z/ 1.16.2 Thrust Reverser Advisory Lights

S i x thrust reverser advisory l i g h t s a r e located i n f ront and t o the r i g h t of the p i l o t , s l i g h t l y below eye leve l . These l i g h t s a r e attached

center of the instrument panel shroud v isor . When they a r e i l luminated, to the underside of the radio cont ro l heads which a r e mounted i n the

the l i g h t s read, from l e f t t o r i g h t : LH T/R ARM; LH T/R LTNLOCK: LH ' i / K DEPLOY; RH T/R ARM, RH T/R UNLOCK; RH T/R DEPLOY. 2/

long a s the th rus t reverser cont ro l switch i s i n the ON pos i t ion and the The amber LH and RH T/R ARM l i g h t s , which i l lumina te and s tay on a s

engine power levers a r e a t IDLE, ind ica te tha t e l e c t r i c a l power is ava i l - able fo r th rus t reverser deployment. I f e i t h e r ARM l i g h t comes on i n f l i g h t , the master caut ion l i g h t w i l l a l so i l luminate .

The red LH and RH T/R UNLOCK l i g h t s w i l l come on when the respec t ive t h r u s t reverser doors a re not completely stowed or the secondary lock i s not i n the engaged (locked) posi t ion. I f e i t h e r UNLOCK l i g h t comes on i n f l i g h t , the master caut ion l i g h t w i l l a l so i l luminate .

reverser doors a r e f u l l y deployed. The blue LH and RH T/R DEPLOY l i g h t s come on when the th rus t

breaker. Deactivation of the c i r c u i t breaker removes the e l e c t r i c a l power needed t o i l luminate the indicator l i g h t s and the master caut ion l i g h t protected by the breaker.

The th rus t reverser ind ica tor l i g h t c i r c u i t is protected by a c i r c u i t

Bul le t in 73-6. Compliance with t h i s b u l l e t i n is mandatory and requi res removal of the UNLOCK and DEPLOY l i g h t s from the d i m i n g c i r c u i t so tha t they w i l l be bright a t a l l times.

After the accident , Rockwell In te rna t iona l issued Sabrel iner Service

The T/R advisory l i g h t s and c i r c u i t breakers were not recovered

by impact and f i r e . from the wreckage, s ince the a rea i n which they were located was demolished

1.16.3 Thrust Reverser Control Switch

A three- posi t ion th rus t reverser con t ro l switch is located on the l e f t s ide of t he engine switch panel. The engine switch panel i s located on the center pedes ta l , j u s t a f t of the th rus t l evers . When the switch

- 2/ Excerpted from Rockwell In te rna t iona l Report NA-67-374. - 3/ LH - left-hand, RH - right-hand, T/R - t h rus t reverser .

- 9 -

i s i n the ON pos i t ion (forward), electrical power. is ava i lab le f o r normal operation of the t h r u s t reverser system. When the switch i s i n the OFF posi t ion, a l l e l e c t r i c a l power i s removed from the th rus t reverser system. When the switch i s i n the EMERG STOW pos i t ion , the gear and t h r u s t lever safety switches are bypassed, t h e stow solenoids of both l e f t and r i g h t thrus t reverser hydraulic con t ro l valves a r e energized, and hydraulic pressure i s d i rec ted t o the ac tua to r stow por ts .

A red p l a s t i c sa fe ty cover i s i n s t a l l e d over the switch, which must be l i f t e d t o a c t u a t e the switch t o either the ON or EMERG STOW pos i t ions . (Placing the sa fe ty cover i n t h e down pos i t ion moves the toggle t o the OFF posi t ion) . The switch was not recovered from the wreckage, s i n c e the area i n which i t was located was demolished by impact and f i r e .

1.16.4 Thrust Reverser Lever Stop Assembly

thrus t lever t r a v e l so t h a t maximum allowable t h r u s t i s not exceeded. The s top assembly i s used when a landing i s made a t any f i e l d e leva t ion up t o 2,500 f e e t . Before t h e landing, the app l icab le f i e l d e leva t ion and temperature index markings should be al igned by turning the knurled adjustment knob, as necessary. Above 2,500 f e e t i n e leva t ion , the t h r u s t

stops f o r t h e l e f t - and right-hand reverser piggyback lever were found lever should be actuated only t o the precomputed EPR s e t t i n g . The vernier

set i n a pos i t ion corresponding t o 1,000 f e e t a l t i t u d e and 60' F.' This se t t ing l imited the reverse t h r u s t 15 percent t o 20 percent from what should have been ava i lab le a t Montrose.

The purpose of t h e vernier s top i s t o limit the amount of reverse

1.16.5 Previous Incidents of Unwanted Thrust Reverser Deployment i n F l igh t

ployment involving Sabrel iners . The f i r s t occurred on December 17, 1969, and involved a Model 60, N3600X. Shortly a f t e r t h a t f l i g h t , the p i l o t prepared a wr i t t en statement, a por t ion of which is presented below:

There are two known cases of unwanted i n- f l i g h t t h r u s t reverser de-

"After l i f t o f f the gear was r e t r a c t e d , and l i g h t i n the handle went ou t , t h r u s t r everse rs were placed t o o f f , and the acce le ra t ion was s t a r t e d t o 200 k t s . A s w e passed 800 f t . MSL, I s t a r t e d a l e f t turn t o in te rcep t the radial. A t t h i s time the Master caut ion l i g h t came on. I checked the panel and no l i g h t s were v i s i b l e on i t . I inmediately saw the l e f t th rus t reverse unlock l i g h t was on and seconds later the l e f t th rus t reverser deploy2d.- A t climb power the a i r c r a f t became almost uncontrolable /sis/. My f i r s t r eac t ion was t o con t ro l the a i r c r a f t . Seconds lzter I ra i sed the guard and placed t h e t h r u s t reverser switch t o emergency stow; waited a few seconds f o r something t o happen. The reverser d idn ' t

became more controlable /sic/ but speed and a l t i t u d e were stow. I then snapped t h e l e f t t h r o t t l e t o i d l e . The a i r c r a f t

-

- 10 -

de te r io ra t ing . The tower had noted t h a t we were i n d i f f i c u l t y and ca l l ed us asking i f w e needed ass i s tance . I ins t ruc ted Mr. Woodard t o ask f o r landing. My speed a t t h i s time was 138 k t s and slowly

reverser switch i n arm, backed t o o f f , and then t o emergency stow. losing a l t i t u d e . With f u l l power on t h e r i g h t engine I placed t h e

The reverser stowed, I l e f t the engine i n i d l e and landed-on-runway 34 a t White P la ins without fu r the r incident . On taxing LsicI i n , I armed the reverser and r a n them through and they operated n&nally."

In the inves t iga t ion subsequently conducted by Rockwell I n t e r n a t i o n a l , no c l e a r reason f o r the unwanted reverser deployment was found, although t h r u s t reverser rigging and t h e t h r u s t reverser con t ro l switch were sus- pect . A s a r e s u l t of i ts inves t iga t ion , Rockwell I n t e rna t i ona l issued two mandatory F ie ld Service Bul le t ins , which were implemented on N743R:

1. 69-29 - Engine - Thrust Reverser Rigging Inspection.

2 . 70-6 - Thrust Reverser Control Switch Par t Number 4TLll-1.

The second incident of unwanted reverser deployment occurred on December 19, 1972, and involved a Sabreliner Model 40 , N360N. The i n c i- dent came t o t h e a t t e n t i o n of Board inves t iga to rs during the present inves t iga t ion and t h e p i l o t of N360N was requested t o prepare a w r i t t e n statement. H e s t a ted , i n par t :

"While taxi ing out I went through the prescribed North American c h e c k l i s t , actuated the reverse rs and stowed them with the stow

were out a f t e r using the stow switch. The stow switch was off switch. A l l l i g h t s were normal during deployment and a l l l i g h t s

and switch guarded.

reached 140 knots and the gear had been re t rac ted . A t t h i s point 'We received take off clearance wi th a normal take off u n t i l w e

w e had l o s t the r i g h t engine. . . . I checked t h e engine ins t ru - the re was a l o t of noise and v ib ra t ion and I f i r s t thought t h a t

ment group. These instruments showed normal. Out of t h e corner of my eye, I caught t h e unlock and deploy l i g h t on the r i g h t t h r u s t reverser . I immediately went t o the stow pos i t i on with the reverser switch and reduced power t o i d l e on t h e r i g h t engine. The t h r u s t reverser stowed. During t h i s time I monitored airspeed t o maintain 140 knots o r below 160. The maximum time of emergency was approximately 30 t o 45 seconds.

"After the th rus t reverser stowed, I maintained i d l e power on t h e r i g h t engine and had the co- pi lot p u l l a l l c i r c u i t breakers on t h e th rus t reversers. These c i r c u i t breakers are the rear row on the c o- p i l o t ' s sub-panel. Upon completion, I returned t o climb power on both engines and accelera ted air speed t o indicated 350

- 11 - knots. The t h r u s t reversers remained stowed wi th t h e switch i n the stowed pos i t ion and c i r c u i t breakers pulled.

"continued f l i g h t t o Calgary, Canada and landed with no t h r u s t reversers. On the ground taxi ing i n , I react ivated a l l systems and checked the t h r u s t reversers which act ivated normally."

Likewise, no d e f i n i t e reason could be given f o r the unwanted t h r u s t reverser deployment i n t h i s case.

1.16.6 Operational Information

weight of 15,500 pounds, f i e l d e levat ion of 5,700 f e e t , temperature 68O The following operat ional d a t a were ca lcu la ted , based on a i r c r a f t

F . , (20° C . ) , runway s lope zero, wind ve loc i ty zero, takeoff t h r u s t on both engines, and a i r c r a f t r o t a t i on held t o the recommended 13O takeoff a t t i t u d e during climbout:

FAA required runway length V 1 VR v2 Ground r o l l Distanceto35-foot obstacle Speed a t 35-foot obstacle Height a t 3,500 f e e t

Height a t 7,000 f e e t (distance traveled)

(distance traveled)

5,500 f e e t 104 Knots Indicated Airspeed (KIAS) 111 KIAS 118 KIAS 2,900 f e e t 4,000 f e e t 125 KWS

16 f e e t (approximately)

470 f e e t (approximately)

climb c a p a b i l i t i e s of the Model 60 Sabreliner when one reverser i s deployed and the respect ive engine t h r o t t l e i s re tarded t o i d l e . The assumptions were: the a i rp lane had reached 150 KWS (estimated average speed between obstacle height and end of runway); one engine w a s a t takeoff power; the other engine w a s a t i d l e wi th reverser deployed; the landing gear was re t rac ted ; and the f l a p s were up. Under these condi t ions , Rockwell In te rna t iona l ca lcula ted t h a t the a i rp lane could climb out on a 5 . 7 percent gradient . The heading could be held , using a 8.7' rudder def lect ion (25O was avai lable) and 7' a i l e r o n angle (31" was ava i lab le ) . Eoth the 70 and 31' f igures a r e the sumof the def lec t ion angles of tile two aile- rons. If no control cor rec t ion was appl ied, the yaw angle r e s u l t i n g from the th rus t and drag asymnetry would h e 5.4u. Moreover, i f t h e a i r c r a f t was i n a coordinated, 60°-banked l e f t t u r n , wi th l e f t reverser deployed and the power levers of both engines advanced, the a i r c r a f t would be i n a 2g turn , and would lose speed a t a rate of approximately two knots per second. A t 2g, the a i r c r a f t s tal l speed would be increased by about 40 percent. I f the f l a p s were lowered, drag would have increased, ani any power reduction would have caused a s t a l l almost immediately.

The Board asked Rockwell In te rna t iona l t o comment on the con t ro l and

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1.16.7 Thrust Reverser Emergency Stow Procedure

Manual (dated 12-29-69) contains the following in s t ruc t ion : The emergency procedure sec t ion of the Sabrel iner Airplane F l igh t

"If a t h rus t reverser malfunction i s indicated i n f l i g h t , proceed a s follows:

1. Power l eve l (affected engine) Retard t o IDLE.

2 . THRUST REVERSER toggle switch - EMERG STOW.

3 . Check respect ive LH or RH T/R l i g h t s - Out.

a s follows: "If e i t h e r amber T/R ARM l i g h t only comes on i n f l i g h t , proceed

1. THRUST REVERSER toggle switch - EMERG STOW. Thrust reverser operation w i l l not be ava i lab le u n t i l the toggle switch i s placed back a t Normal (ON) ."

2 . ANALYSIS AND CONCLUSIONS

2 . 1 Analysis

crew incapaci ta t ion. The a i r c r a f t weight and center of g rav i ty were with- The crew was properly c e r t i f i c a t e d , and there was no evidence of

i n prescribed limits. There was no evidence of any malfunction or f a i l - ure of the airframe or systems. Although there was concern tha t the d i r t and rocks from the runway construct ion a c t i v i t y might have caused

vealed tha t both were capable of normal operation. S imi la r ly , t he re was foreign object damage, disassembly of the engines a f t e r the accident re -

no evidence tha t any engine th rus t reverser components had d i s to r t ed before ground impact.

noted what appeared t o be a 30° change of heading t o the r i g h t , which was toward the sho r t e s t rou te to Denver. However, the d i r e c t i o n of the turn reversed to the l e f t , and the l e f t bank angle increased a s the a i r - c r a f t descended t o the ground. Although the reversa l undoubtedly marked the onset of d i f f i c u l t i e s , i t i s not known why the turn and descent continued unchecked.

The takeoff and i n i t i a l por t ion of the climb were normal. Witnesses

condition r e su l t i ng from an unwanted thrus t reverser development tended The f l i g h t t e s t s revealed tha t even though the asymmetrical t h rus t

t o make the a i r c r a f t tu rn i n tha t manner, the a i r c r a f t was con t ro l l ab l e

or maintaining any bank he desired. The p i l o t could have elected t o con- l a t e r a l l y , and the p i l o t should have had no d i f f i c u l t y i n es tab l i sh ing

t inue the turn back t o the a i r p o r t while he was troubleshooting the

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d i f f i c u l t y , bu t , because of h i s i n a b i l i t y t o mi in ta in a l t i t u d e , he would have been more prudent t o have kept a wings- level a t t i t u d e and t o have landed s t r a i g h t ahead i f the d i f f i c u l t y could not have been corrected. Not only was there open and l e v e l t e r r a i n t o t h e north and t o t h e west, but a l s o there were t h e high-tension l i n e s and cons t ruc t ion equipment

promised t h e sa fe ty of an emergency approach. Furthermore, t h e p i l o t between h i s pos i t ion and the a i r p o r t , which would have se r ious ly com-

would have had s l i g h t l y more time t o troubleshoot because of the decrease i n descent rate, due t o a wings- level a t t i t u d e .

The reason fo r the apparent i n a b i l i t y of the crew t o resolve the problem confronting them is d i f f i c u l t t o understand, p a r t i c u l a r l y i n view of the apparent ease with which the p i l o t s involved i n the two previous inc idents i d e n t i f i e d the problem and employed the co r rec t emergency procedure t o el iminate the d i f f i c u l t y .

thrus t reverser deployment i n t h i s acciden may be considered: Three explanations f o r t h e ca tas t rophic r e s u l t s of t h e unwanted

,d a The crew was unable t o iden t i fy the problem;

a the crew iden t i f i ed t h e problem, but could not g e t emergency stow system to work; o r

the crew i d e n t i f i e d the problem, but used improper emergency procedures i n an attempt t o co r rec t the s i t u a t i o n .

It is very unl ike ly t h a t t h e crew f a i l e d t o no t i ce t h e v ib ra t ion and turning of the a i r c r a f t t h a t would have indicated some d i f f i c u l t y , e i the r with the f l i g h t con t ro l s or with the engines. A quick scan of the instrument panel should have eliminated any concern about an impend- ing engine f a i l u r e . Thus, i f t he re were no indica t ions t o the cont rary ,

cont ro ls , which would have prompted them t o continue the turn back t o the crew might have assumed t h a t there was some problem wi th the f l i g h t

the a i r p o r t , and t o lower t h e f l a p s i n an e f f o r t t o a l ter the configura- t ion and improve c o n t r o l l a b i l i t y . There are two d i f f i c u l t i e s , however,

had a ser ious e f f e c t on the a i r c r a f t acce lera t ion and climb performance. i n the way of t h i s assumption. F i r s t , a con t ro l problem should not have

Second, there i s only one way the a c t u a l emergency s i t u a t i o n would not have been indicated on t h e instrument panel. I f the c i r c u i t breaker pro- tecting t h e th rus t reverser indica tor c i r c u i t were inopera t ive , the various reverser indica tor l i g h t s and the master caut ion l i g h t , i n tu rn , would f a i l t o i l luminate. There was no evidence t o suggest t ha t t h i s c i r c u i t breaker was inoperat ive. In f a c t , t h e p i l o t s had used the reverser system during the preceding landing, apparently without d i f f i c u l t y . Moreover, a l l appropriate switches were tes ted a f t e r the accident , and they operated normally. The Board concludes t h a t the LH unlock, LH T/R deploy l i g h t s , and, i n t u r n , themaster caut ion l i g h t d i d i l luminate duringtheemergency.

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f a i l ed momentarily t o have seen, the l i g h t s (located s l i g h t l y below the The p i l o t s might have had d i f f i c u l t y detectfng, or might have

which was f a i r l y low on the horizon. The l igh t ing conditions might have g l a re shield) because of the sun. The f l i g h t was turning toward the sun,

been such tha t the LH unlock and the LH T/R deploy l i g h t s were not read i ly discernible; however, the considerably la rger master caut ion l i g h t should have been eas i e r t o see , and should have a l e r t ed the crew t o the problem with the other warning l i g h t s . Accordingly, the pos i t ion of the sun r e l a t i v e t o the cockpit should have delayed evaluation of the problem only momentarily, i f a t a l l .

cedure, i t i s possible tha t a malfunction i n the th rus t reverser system prevented the reverser doors from stowing. However, a l l mechanical reverser components were funct ional ly tes ted and were found capable of normal operation. Even i f the emergency stow switch had malfunctioned,

would have enabled the crew to climb, i f necessary, and t o r e tu rn fo r a a reduction i n th rus t on the engine i n the reverse th rus t configurat ion

malfunction of the thrus t reverser system prevented the crew from con- s a f e landing. The Board concludes tha t ne i the r e l e c t r i c a l nor mechanical

t r o l l i n g the a i r c r a f t safely.

Once the crew iden t i f i ed the problem and followed the emergency pro-

proper cor rec t ive procedures for an unwanted deployment of the th rus t It i s the conclusion of the Board tha t the crew d i d not know the

reverser i n f l i g h t , desp i te t h e i r years of p i lo t ing experience and t h e i r spec i f i c qua l i f i ca t ion i n the Sabrel iner . The crewmembers were primarily f l i g h t i n s t ruc to r s i n the Boeing 7 2 7 , and, l i k e severa l other f l i g h t in- s t r u c t o r s , they flew the Sabreliner only a t random, a s company needs required. The t o t a l accumulated f l i g h t time for the cap ta in i n the Sabre- l i n e r was r e l a t i v e l y low, averaging approximately 9 hours a month. The

dure for i n- f l igh t stowage of the th rus t reverser was discussed i n ground first o f f i ce r averaged fewer than 7 hours a month. Although the proce-

power s e t t i n g was not s t ressed . The procedure was a l so described i n the t ra in ing , the f a c t tha t the reverser w i l l not stow i n f l i g h t a t a high-

f l i g h t manual; however, i t was considered a Phase 2 emergency, which meant tha t immediate ac t ion was not necessary; a s a r e s u l t , the procedure usually was not memorized.

I n t h i s instance, the crew was faced with a loss of a l t i t u d e and airspeed approximately 1,000 f e e t above the ground which, according t o the a i r c r a f t performance da ta , would have continued a s long a s the l e f t engine remained a t a high-power se t t i ng . A s might be expected, the crew would no t consider a reduction of power t o co r r ec t fo r a loss of a l t i -

ca l led for an appropriate reduction i n power. tude and airspeed unless they were aware of the emergency procedure which

apparently had lowered the f l aps dur ing the turning descent , possibly i n The landing f l aps were found i n the extended pos i t ion . The p i l o t

an e f f o r t t o lower the s t a l l speed. However, the f l aps (which on t h i s

- 15 - model a i r c r a f t primarily increase drag) only aggravated the cont ro l problem. A s indicated by the Rockwell In te rna t iona l performance ca lcu la t ions , extension of the f l aps under these circumstances very l i k e l y induced, ra ther than prevented, a s t a l l condi t ion during the f i n a l seconds of f l i g h t .

Ekamination of the engines a f t e r the accident produced s u f f i c i e n t evidence t o i nd ica t e tha t they were a t i d l e t h rus t a t impact. It is

circumstances, retarded the th rus t levers j u s t before the a i r c r a f t logical t o conclude tha t the p i l o t , reac t ing normally t o the c r i t i c a l

gency stow pos i t ion a t t h i s time. crashed. Undoubtedly, the reverser cont ro l switch was not i n the emer-

2.2 Conclusions

(a) Findings

The crewmembers were c e r t i f i c a t e d t o conduct t h i s f l i g h t .

The a i r c r a f t was c e r t i f i c a t e d , and the gross weight and center of g rav i ty were within prescribed limits.

There was no evidence of any f a i l u r e or malfunction of the airframe or a i r c r a f t systems, nor was there any f i r e i n f l i g h t .

The l e f t engine reverser was deployed, the f l aps were down, and the engines were a t i d l e when the a i r c r a f t crashed.

In- f l igh t reverser deployment caused buf fe t ing , but the a i r c r a f t was cont ro l lab le .

When the th rus t reverser doors were deployed i n f l i g h t

would not stow, and the a i r c r a f t d i d not maintain a l t i t u d e and the reversed engine developed high power, the doors

and a i r speed.

could have climbed with the r i g h t engine a t climb power, Performance da ta based on t h i s takeoff i nd ica t e tha t N743R

provided the l e f t engine was at IDLE.

There was no evidence of warning l i g h t malfunction.

reverser deployment. The crew should have been aware of the unwanted th rus t

The crew d i d not know the proper cor rec t ive procedure f o r the emergency.

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(b) Probable Cause

The National Transportation Safety Board determines tha t the probable cause of t h i s accident was the continued operation of the l e f t engine a t climb power a f t e r an unwanted in- f l igh t deployment of the l e f t engine th rus t reverser , which resu l ted i n a de t e r io ra t ion of a i r c r a f t performance.

3 . RECOMMENDATIONS AND CORRECTIVE ACTION

(a) Corrective Actions

Soon a f t e r the accident , the Federal Aviation Administration (FAA)

American Rockwell Model NA-265-40, - 60, and -70 a i rp lanes . The AD re- issued a te legraphic Airworthiness Direct ive (AD) t o a l l owners of North

quired the thrus t reversers t o be stowed and locked i n the forward th rus t posi t ion. The telegram s t a t ed tha t t h i s was an inter im measure and tha t f i n a l d i spos i t ion of the r e s t r i c t i o n would depend on the r e s u l t s of tests and inves t iga t ions then i n process.

a l l Sabreliner operators bringing t o t h e i r a t t e n t i o n the r e s u l t s of the Rockwell In te rna t iona l issued a "Sabre Gram" dated May 2 , 1973, t o

f l i g h t t e s t s i n r e l a t i o n t o the c o n t r o l l a b i l i t y of the a i r c r a f t with unwanted th rus t reverser deployment i n f l i g h t . The Sabre Gram s t a t e d , i n pa r t :

"The f l i g h t t e s t evaluation . . . has been completed using a Ser ies

permit th rus t reverser deployment with gear up fo r the tests. This 60 Sabreliner i n Type Design configuration except f o r rewiring to

a i rp iane was chosen a s represen ta t ive of a l l th ree models. Test lsisf were flown i n a represen ta t ive s e r i e s of conditions: gear ex-

Test speeds covered the range of 110 t o 200 knots , wi th t e s t po in ts tended, gear r e t r a c t e d , wing f l aps up, and wing f l aps f u l l y extended.

a t 20 knot i n t e r v a l s between 140 and 200 knots. Tests were conducted i n the a l t i t u d e range of 10,000 t o 6,000 f e e t . The t e s t s resu l ted i n Sabreliner F l igh t Test P i l o t , RUSS Sco t t , terming con- t r o l l a b i l i t y EXCELLENT a t any speed from 140 knots upward. A selected heading could be held, or could be trimed hands o f f , and 30° bank turns i n t o and away from the reverse t h r u s t engine could be made at w i l l , with ample cont ro l movement i n reserve. Below 140 icnots,controlrequirements progressively increase, f u l l rudder de- f l e c t i o n being required t o hold a heading a t 110 knots."

The F:J, issued AD 73-12-9, Amendment 39-1664, which became e f f e c t i v e June 16, 1973. This AD required accomplishment of one of th ree a l t e rna- t ives p r i o r to fur ther f l i g h t of Model NA-265 th rus t reverser equipped airplanes:

1. The a i r c r e f t can be operated i f the reversers a r e stowed and locked a s required by the te legraphic AD.

- 17 -

2 . The a i r c r a f t can be operated i f :

(a) Revisions dated May 16, 1973, a r e incorporated i n the NA-265 s e r i e s Sabrel iner Airplane F l i g h t Manuals approved by the FAA. These rev i s ions require : a v i sua l inspect ion of each th rus t r everse r "8" hook f o r proper engagement before each f l i g h t ; the t h r u s t reverser con t ro l switch be i n the EMERG STOW pos i t ion before takeoff , and remain i n t h a t pos i t ion u n t i l t h e a i r c r a f t reached 1,500 f e e t above ground l eve l ; t h e th rus t reverser con t ro l switch be placed i n the EMERG STOW pos i t ion before placing the

check of the t h r u s t reverser system should be made a f t e r landing gear handle a t DOWN f o r landing; and operat ional

each f l i g h t . The emergency procedures sec t ion (Section 11, page 19) contains these notes: "An inadver tent t h r u s t r everse r deployment i n f l i g h t w i l l r e s u l t i n heavy buf fe t which decreases as the respect ive engine t h r u s t is de- creased. The a i r c r a f t is r ead i l y con t ro l l ab le , hcwever, a l t i t u d e cannot be maintained u n t i l t h r u s t i s reduced on the engine with the deployed t h r u s t reverser. I f the th rus t reverser f a i l s t o stow a f t e r placing the t h r u s t reverser con t ro l switch i n the ENERG STOW pos i t ion , shut down the respect ive engine and land a s soon a s pract icable ."

(b) Certa in p r e f l i g h t inspect ions a r e performed.

(c) Cer ta in inspections of the th rus t r everse r system a r e performed a t 100- and 300-hour i n t e r v a l s .

(d) The dimming c i r c u i t is modified so t h a t the T/R advisory l i g h t s cannot be dimmed.

3 . The a i r c r a f t can be operated i f equivalent inspect ions , mainten-

A i r c r a f t Engineering Division, FAA Western Region. ance procedures, and i n s t a l l a t i o n s are approved by the Chief ,

(b) Recommendations

A review of the Rockwell In te rna t iona l Sabreliner Model 60 t h r u s t reverser system and regula t ions governing th rus t reverser systems was

resulted from t h i s review exceeded t h e scope of the measures required in€ t i a ted a s a r e s u l t of t h i s accident. Since c e r t a i n proposals which

by AD 73-12-9, Amendment 39-1664, the National Transportat ion Safety Board reconmends t h a t the Federal Aviation Administration amend Airworthi- ness Directive 73-12-9 to:

1. Require modification of the t h r u s t reverser system f o r t h e Rockwell In te rna t iona l Sabreliner Model 60 which would minimize

- 18 - reverser system dependence upon r igging tolerances t o insure proper ind ica tor l i g h t operation. In any modification, se r ious considerat ion should b e given to:

(a) Incorporation of a microswitch i n the th rus t reverser ac tua tor to cont ro l the unlock l i g h t .

(b) Relocation of the present unlock l i g h t microswitch from

in unlock l i g h t deact ivat ion only upon pos i t i ve physical the secondary l a t ch solenoid to a pos i t ion which r e s u l t s

engagement of secondary l a t ch and reverser door s t r i k e s . (A-73-107)

2 . Incorporate a stowing function i n the Sabrel iner reverser SYS- tern which would automatically stcw a deployed th rus t reverser when the t h r o t t l e is not i n the i d l e pos i t ion . (A-73-108)

BY THE NATIONAL TRANSPORTATION SAFETY BOARD:

f sf JOHN H. REED Chairman

/ s f FRANCIS H. McADAMS Member

/ s f LOUIS M. THAYER Member

/ S f ISABEL A. BURGESS Member

/ s f WILLIAM R. HALEY Member

November 7 , 1973

- 19 - APPENDIX A

INVESTIGATION AND HEARING

1. Investigation

The National Transportation Safety Board received notification of

were dispatched immediately from the Denver Field Office. They were the accident at approximately 1800 on April 13, 1973. Two investigators

A fifth investigator was dispatched from the Los Angeles Field office joined the following day by two investigators from the Washington Office.

headquarters in Los Angeles. to conduct an examination of maintenance records at Continental Airlines

Structures, Systems, Powerplants and Maintenance Records.

2 . Hearing

Investigative groups were established for Operations, Witnesses,

There was no public hearing held in connection with this investigation.

- 20 - APPENDIX B

CREW INFORMATION

l i n e s as an ins t ruc to r p i l o t . He was hired by the company on January 9 ,

Transport P i l o t C e r t i f i c a t e No. 1638576 with r a t i n g s f o r a i rp lane multi- 1967, and served as a l i n e p i l o t u n t i l January 1, 1972. H e held Airline

engine land, with type r a t i n g s i n the Boeing 727 and the NA-265 (Sabre- l i n e r ) , and c o m e r c i a l p r iv i l eges f o r a i rp lane multiengine land, Boeing

March 23, 1973, with no l imi ta t ions . Company records ind ica te t h a t Cap- 707/720. H i s l a t e s t FAA f i r s t - c l a s s medical c e r t i f i c a t e was issued on

June 2 7 through June 30, 1972. From July 18 through July 25, 1972, Captain Walsh t a i n Walsh received 24 hours of Sabreliner i n i t i a l t r a in ing (ground) from

received 6hours 12minutesof f l i g h t i n s t r u c t i o n , o fwh ich lhou r 15minuteswere

p i l o t time, of which 83 hours 43 minutes were i n the Sabrel iner , and 28 used for a r a t i n g r ideg ivenby anFAA inspector. Hehad a t o t a lo f10 ,000 hours'

hours 25 minutes were i n the Sabreliner during the 90-day period preceding the accident.

Captain Robert Morah Walsh, aged 37, was employed by Continental A i r -

Captain James Louis Ford, aged 33, was employed by Continental Air-

a s a l i n e p i l o t u n t i l November 1, 1972. H e held A i r l i ne Transport Certi- l i n e s as an i n s t r u c t o r p i l o t . He was hired on March 8, 1965, and served

f i c a t e No. 1524586, with r a t i n g s f o r a i rp lane s ingle- and multiengine

mercial p r iv i l eges f o r a i rp lane single-engine land. His l a t e s t FAA f i r s t - land with type r a t i n g s i n Boeing 707, 720, 727, and the NA-265, and com-

class medical c e r t i f i c a t e was issued on October 4 , 1972 , wi th no limita-

Sabrel iner i n i t i a l t ra in ing (ground) from September 12 through September t ions , Company records ind ica te t h a t Captain Ford received 24 hours of

15, 1972. From September 20 through October 3 , 1972, Captain Ford received 4 hours h5 minutes of f l i g h t ins t ruc t ion , and a r a t i n g r i d e of 1 hour 28 minutes, given by an FAA inspector . Captain IJalsh accompanied Captain Ford as a check p i l o t on t h i s f l i g h t . He had a t o t a l p i l o t time of 7,317 hours 27 minutes of which 26 hours 18 minutes were i n the Sabre- l i n e r . Fourteen hours 23 minutes were i n the Sabreliner during the 90- day period preceding the accident.

- 2 1 - APPENDIX C

AIRCRAFT INFORMATION

Aircraft Data

The airplane, a Sabreliner Model NA-265-60, was manufactured by North American Aviation, Inc. (now doing business as Rockwell Inter- national), under serial No. 306-11. It was assigned U. s. Registry No. 743R. Manufacture was completed on March 26, 1968. The total flying time was 2,372 hours 5 minutes.

gine serial numbers and times were as follows: N743R was equipped with two h'att & Whitney JT12A-8 engines. En-

Date of Mfg. S /N Total Time T.S.O.

Left 2-1-68 P673095NB 2,241:50 Right 1-27-68 P673096NB 2,213:03 703 :24

732 : 11

as pertinent Service Bulletins issued by the manufacturer, had been com- plied with.

All pertinent Airworthiness Directives issued by the FAA, as well

file no.3-0520 · file no. 3-0520 national transportation safety board washington, d. c. 20591...

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