holding patterns -101: a new and novel approach to understanding the pitfalls and misconceptions of...
TRANSCRIPT
Holding Patterns -101: A New and Novel Approach to Understanding the Pitfalls and
Misconceptions of Timing and Wind Correction in the Holding Pattern
Part 1Les Glatt, Ph.D.
ATP/CFI-AI AGI/IGIVNY FSDO FAASTeam Representative
(818) 414-6890
June 25, 2013
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Why Do We Need to be Proficient in Flying the Holding Pattern?
• If undergoing training for an instrument rating the Instrument PTS (Jan 2010) as per section III.C(8) states – “Uses proper wind correction procedures to maintain the desired
pattern and to arrive at the fix as close as possible to a specified time”
• Maintaining “Instrument Experience” as per FAR 61.57 C(1(ii)) requires the pilot to fly at least one holding pattern over the last 6 months
• Undergoing a Instrument Proficiency Check (IPC)– Standards are the same as PTS for a new instrument rating
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An Observation
• When performing instrument proficiency checks I have found that when the winds are stronger then about 10 knots many pilots seem to have problems converging to the correct holding pattern
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Is there a Common Factor that Comes into Play that is the Cause of this Problem?
Answer is Yes
• Because trying to nail the holding pattern down is based on the “Trial and Error” method!
• Many CFII’s and the FAA provide “Rules of Thumb” for timing and wind corrections while flying a holding pattern– However these “Rules of Thumb” usually have limitations that
are never provided to the student or instrument pilot by either the CFII or the FAA
• Attempting to uses these “Rules of Thumb” under all circumstances can lead to pilot frustration and a significantly longer time trying to converge to the correct holding pattern
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When any Pilot is Performing a Maneuver that is Based on the “Trial and Error”
Method It is Necessary to Have a Deeper Understanding of the Maneuver in Order to Eliminate any Pitfalls and Misconceptions!
Objective of Seminar
• Provide you with the information you need to understand the limitations of the AIM recommendations for timing and wind correction in a holding pattern
• Develop a methodology to allow the pilot to get established in the correct holding pattern with a minimum number of circuits
• Develop a set of charts (“Holding Pattern Solution”) which tells the pilot what the exact inbound wind correction angle, outbound heading and outbound time should be to allow the aircraft to re-intercept the inbound course with a one minute inbound leg
• Use of the GPS to provide the “Holding Pattern Solution” to the pilot prior to turning outbound
Agenda
• Holding pattern requirements• Parameters that control the holding pattern ground track• The “Holding Pattern Solution”• Limitations of the AIM recommendations for outbound timing and
outbound wind correction angle• Understanding the “Type 1” and “Type 2” holding patterns• Why it can take a few circuits to converge to the correct outbound time
and outbound wind correction angle• Developing a “Corrective Action Table” which informs the pilot how to
modify the outbound heading and time in order to converge to the “Holding Pattern Solution”
• How to Converge to the “Holding Pattern Solution” on the second circuit• Automating the “Holding Pattern Solution” to the GPS • Summarize
When Will We Be Required to Fly a Holding Pattern?
• ATC may have requested you to hold because of delays at your airport of intended landing
• Need to hold due to lost communications• You may request a hold because you are not prepared to
execute the approach– Equipment malfunction– Single-pilot operation
• Pilot is not ready to execute the approach?
No Matter What the Reason for Holding
Pilots Should Use this Time in the Holding Pattern to Prepare for the Approach
Pilot Actions During Holding
• Reference – Airman Information Manual (2013)– Make all turns during entry and holding
• 3 degrees/sec, or• 30 degree bank angle, or• 25 degree bank if using a flight director• Use whichever requires the least bank
– Standard rate turn at a 30 degree bank angle will occur at 210 KTAS– Standard rate turn at a 25 degree bank angle will occur at 170 KTAS
– Maximum KIAS for holding • MHA-6000 feet- 200 KIAS• 6001-14000 feet – 230 KIAS• 14001 feet and above – 265 KIAS• May be exceptions to the above maximum KIAS
– Compensate for the wind effect primarily by drift correction on the inbound and outbound legs.
• When outbound triple the inbound drift correction (the “M-Factor”)
Pilot Actions During Holding (Cont.)
– Timing • Inbound timing
– At and below 14000MSL – 1 minute leg– Above 14000MSL – 1 ½ minute leg
• Outbound timing– Begins over/abeam the fix, whichever occurs later– If unable to determine abeam point start outbound timing when
outbound turn is completed
IT IS ALWAYS BENEFICIAL TO START WITH UNDERSTANDING THE “SIMPLE” AND
THEN MOVE TOWARD UNDERSTANDING THE “COMPLEX”
If We are Going to Try to Understand the Actual Complexity of the Holding Pattern in the Presence of a
Wind
We Can Begin by Trying to Understand the Parameters that Affect the Actual Shape and Extent of the Holding
Pattern
Parameters that Effect the Holding Pattern Ground Track
• How do we determine the parameters that effect the holding pattern ground track?– Need to understand the wind triangle
• Most pilots utilize an electronic flight computer or a E6B flight computer
– Utilizing either of these tools does not allow the pilot to understand the parameters that control the wind correction angle and the groundspeed
– Pilots do not need these tools to understand the wind triangle solution
Parameters the Effect the Holding Pattern Ground Track(Cont.)
– The results of the wind triangle provide the parameters that control
• Ground track of the holding pattern• Inbound wind correction angle• Outbound heading• Outbound time
Solution of the Wind Triangle Problem
What is the Wind Triangle and How Does it Help Us Understand the Holding Pattern?
• Given the VTAS, wind speed and direction– Determine the wind correction angle (WCA) and ground speed
• How do we develop the wind triangle?
Desired Track
VG
VTAS
VWind
𝜎
Heading
= Angle between desired course and wind direction
s = Wind correction angle(WCA)
VG = Ground Speed
VW = Wind Speed
Understanding Vectors and Components
• Components of the velocity vector
• Right triangle relationships
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VX_WIND
VH_WIND
VWind
Sin V VWINDWIND-X
Cos V VWINDWIND-H
Tan Cos
Sin
V
V
WIND-H
WIND-X
The “Law of Sines” and the Solution of the Wind Triangle
A B
A B C
Sina Sinb Sinc
C
b a
c
180
Sum of the angles of a triangle
degreesa b c h
What is the Wind Triangle Solution?
• Applying the “Law of Sines” to the wind triangle
Wind TAS GV V V
Sin Sin Sin
( )Wind
TAS
G
TAS
VSin Sin
V
V Sin
V Sin
Wind Component Normal toThe Inbound Course
Wind Triangle (Cont.)
• Final solution to the wind triangle is
• Two parameters that control the outcome of the wind triangle
– Wind direction relative to the desired course-
– Ratio of the wind speed to the true airspeed-
Wind
TAS
G Wind
TAS TAS
VSin Sin
V
V VCos Cos
V V
Wind
W
TAS
VV
V
Determining the Wind Speed and Direction(The Inverse Problem)
• How do we determine the wind speed and direction knowing the ground speed and WCA? – Tracking radial or inbound course provides the WCA (Sin)– Knowing the ground speed and the WCA provides
– Using
G
W
TAS
VV Cos Cos
V
W
W
A Sin V Sin
B V Cos
W
ATan
BA B
VSin Cos
The Parameters that Control the Holding Pattern
• Shape of the holding pattern is controlled by– Wind speed ratio– Wind direction relative to the inbound course of the holding
pattern– Provides the
• Inbound wind correction angle• Outbound heading • Outbound time
• Actual dimensions of the holding pattern (what the radar controller sees on his console) will also depend on VTAS – Ground speed and wind speed are divided by VTAS
• Need to multiply the ground speed and wind speed ratios to get actual ground speed and wind speed to obtain the exact dimensions of the holding pattern
• Increasing the VTAS by 10% increases the extent of the holding pattern by 10%
Table of Sines and Cosines
(degrees) Sin Cos0/360 0 1
30 0.5 0.866
60 0.866 0.5
90 1.0 0
120 0.866 -0.5
150 0.5 -0.866
180 0 -1
210 -0.5 -0.866
240 -0.866 -0.5
270 -1 0
300 -0.866 0.5
330 -0.5 0.866
2 2 1Sin Cos