kevin j. renze, ph.d. · pitch control elevator travel center of gravity. pitch control assessment....

Kevin J. Renze, Ph.D.Kevin J. Renze, Ph.D.Airplane PerformanceAirplane Performance

Elevator Control Authority Investigation

Elevator Control Authority Investigation

• FDR data from 84 previous flights operated with the accident airplane

• Beechcraft 1900D simulation

• FDR data from 84 previous flights operated with the accident airplane

• Beechcraft 1900D simulation

Elevator Travel RangeElevator Travel Range

-22-20-18-16-14-12-10

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10121416182022

-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22

ANU ACTUAL ELEVATOR (DEG.) AND

AN

D F

DR

EL

EV

AT

OR

(D

EG

.)A

NU

BEFORE MAINTENANCECONTROL CHECK

FLIGHT


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10121416182022

-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22


AN

D F

DR

EL

EV

AT

OR

(D

EG

.)A

NU

BEFORE MAINTENANCE

FLIGHT TEST

14.7º (AND)

21º (ANU)


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-8-6-4-202468

10121416182022

-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22


AN

D F

DR

EL

EV

AT

OR

(D

EG

.)A

NU

BEFORE MAINTENANCE

AFTER MAINTENANCE

7º (AND)

SHIFT

FLIGHT TEST

14.7º (AND)

21º (ANU)

21º (ANU)


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10121416182022

-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22


AN

D F

DR

EL

EV

AT

OR

(D

EG

.)A

NU

BEFORE MAINTENANCE

AFTER MAINTENANCE

7º (AND)

SHIFT

FLIGHT TEST

14.7º (AND)

21º (ANU)

21º (ANU)

ELEVATOR TRAVEL LOSS

Beechcraft 1900D SimulationBeechcraft 1900D Simulation

• Engineering models provided by RAC

• Implemented in NTSB simulation tools

• Validated against Beechcraft 1900D flight test data

• Engineering models provided by RAC

• Implemented in NTSB simulation tools

• Validated against Beechcraft 1900D flight test data

-20-15-10-505

101520

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101520

FLIGHT AFTER MAINTENANCE

AIRPLANE NOSE UP

Elev

ator

(Deg

rees

)

Time (Seconds)

FDR ELEVATOR

FLIGHT BEFORE MAINTENANCE

SIMULATION ELEVATOR

AIRPLANE NOSE UP

Elev

ator

(Deg

rees

)

Time (Seconds)

FDR ELEVATOR

SIMULATION ELEVATOR

Beechcraft 1900D Simulation ResultsBeechcraft 1900D Simulation Results

Takeoff Roll

Rotation Climb

Takeoff Roll

RotationClimb

SHIFT

Flight 5481 Simulation ResultsFlight 5481 Simulation Results

• The elevator was restricted to 8º downward

• 9.5º downward elevator was needed

• 7º downward elevator needed if CG within limits

• Balance is critical pitch control factor, not weight

• The elevator was restricted to 8º downward

• 9.5º downward elevator was needed

• 7º downward elevator needed if CG within limits

• Balance is critical pitch control factor, not weight

ConclusionsConclusions• Maintenance changed the pitch control

system

• Elevator was restricted to about half its downward travel• FDR data analysis (7º downward)• NTSB simulation (8º downward)

• 9.5º downward elevator needed• 7º downward elevator needed if CG within

limits

• Maintenance changed the pitch control system

• Elevator was restricted to about half its downward travel• FDR data analysis (7º downward)• NTSB simulation (8º downward)

• 9.5º downward elevator needed• 7º downward elevator needed if CG within

limits

Airplane Weight and BalanceAirplane Weight and Balance

• Air Midwest program

• Component load buildup

• Takeoff ground roll analysis

• Air Midwest program

• Component load buildup

• Takeoff ground roll analysis

Flight 5481 Weight and BalanceFlight 5481 Weight and Balance

11,000

12,000

13,000

14,000

15,000

16,000

17,000

18,000

0 5 10 15 20 25 30 35 40 45 50 55 60

CENTER OF GRAVITY (%MAC)

AIR

PLA

NE

WEI

GH

T (L

BS)

CALCULATEDACTUAL

APPROVED ENVELOPE

Average Weight ComparisonAverage Weight Comparison

30253025Checked bag

--2025Carry-on bag checked planeside

195185200175Passenger andcarry-on bags/ personal items

Interim (lb)Old (lb)New (lb)Old (lb)ComponentFAA GuidanceAir Midwest1

1 Limited carry-on program1 Limited carry-on program

Improved Weight and BalanceImproved Weight and Balance

11,000

12,000

13,000

14,000

15,000

16,000

17,000

18,000

0 5 10 15 20 25 30 35 40 45 50 55 60

CENTER OF GRAVITY (%MAC)

AIR

PLA

NE

WEI

GH

T (L

BS)

NEW PROGRAM

ACTUAL

APPROVED ENVELOPE

Weight and Balance ConcernsWeight and Balance Concerns

• Average Weight Error Sources – Understated average weights– Heavy bags– Variance in actual weight and weight distribution

• Average weight programs need improvement

• Actual weight and location data could eliminate these errors

• Average Weight Error Sources – Understated average weights– Heavy bags– Variance in actual weight and weight distribution

• Average weight programs need improvement


Pitch Control AssessmentPitch Control Assessment

AdequateNormalIn LimitsPre D6 Flights

Pitch ControlElevator Travel

Center of Gravity


CriticalRestrictedIn Limits9 Post D6 Flights



Center of Gravity


MarginalNormalSignificantly Aft

Accident Loading, Normal Elevator




Center of Gravity


AccidentNormalExtremely Aft

Beech 1900C Homer, AK 1987






Center of Gravity


AccidentRestrictedSignificantly AftFlight 5481

AccidentNormalExtremely Aft

Beech 1900C Homer, AK 1987






Center of Gravity

ConclusionsConclusions• Air Midwest’s program did not detect the

significantly aft CG

• Unacceptable errors still exist in average weight programs and require improvements


• The significantly aft CG and restricted elevator resulted in a loss of pitch control

• Air Midwest’s program did not detect the significantly aft CG

• Unacceptable errors still exist in average weight programs and require improvements


• The significantly aft CG and restricted elevator resulted in a loss of pitch control

kevin j. renze, ph.d. · pitch control elevator travel center of gravity. pitch control assessment....

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