Wednesday, January 14, 2015

Instrument flight tips and rules of thumb

When training for probably the most important ticket you will earn (after your private), the volume of information is significant. Here is a bit of knowledge and rules of thumb that may help you...


Taxi Instrument Check [FLOW]

1. pitot-static instrument check

A. airspeed indicator –

i. on zero

ii. Note which scale (outside or inside) reads in knots.

B. altimeter –

i. Confirm that the altimeter is correctly set to the current ASOS, AWOS, ATIS etc.

ii. Then confirm that the altimeter reads within 75 feet of the field elevation.

C. vertical speed indicator – on zero (If not, note the level reference.)

2. gyroscopic / magnetic instrument check

(This part may only be accomplished while making a taxi turn.)

A. attitude indicator – erect, with no more than 5 degrees of lean during a level taxi turn

B. heading indicator – numbers increase on right turn / decrease on left turn

C. magnetic compass –

i. full of fluid

ii. erect

iii. numbers increase on right turn / decrease on left

D. turn coordinator / inclinometer –

i. Miniature airplane leans in direction of turn.

ii. Ball moves to the outside of the turn.

Execute this check and methodically. If any of your primary flight instruments does not appear to be fully functional and reliable, return to the ramp. This is especially true when preparing to fly in actual instrument conditions, particularly at night and/or in turbulence.


􀃖DO NOT descend below circling MDA until within about 30 degrees of the extended runway centerline and landing is assured, meaning that a normal final glide to the runway is possible. Most pilots tend to start their descent much too early and way too far out! Wait until you are close to the runway and almost aligned with it.

􀃖WARNING! Circling approaches are very dangerous, especially at night; the NTSB statistics make this quite clear. Use extreme caution and do it by the book.


􀃖If holding over or in the vicinity of an airport, obtain ASOS, AWOS or ATIS as soon as practical.

􀃖Correctly tune and identify all navaids required for the holding procedure.

􀃖Remember that you never want to “hurry to a hold.” If you slow down before you get to the holding fix . . . maybe you won’t have to hold when you get there! Or maybe you’ll only have to make 1 or 2 orbits instead of 6 or 7. In any case, there is no advantage to flying a hold fast.

􀃖Select and use a recommended entry procedure (direct, parallel or teardrop) that makes sense and which keeps you within the protected holding pattern airspace. Any entry method is fine as long as it does not take you onto the “wrong side,” into the unprotected airspace.

To get the bank angle for a standard-rate (2 minute) turn, divide your airspeed in knots by 10 and add For example, if your airspeed is 120 kt, your bank angle will be 19°

VHF and UHF transmitters work by line-of-sight. To calculate the maximum line-of-sight distance over the horizon in nautical miles for receiving a VHF or UHF radio signal (such as ATC or a VOR or DME transmitter), use 1.23 * sqrt(deltaAltitude_ft)

For example, if your plane is 10,000 ft higher than a VOR transmitter, you will have a good chance of picking it up from 123 nm away (1.23 * sqrt(10,000)). If you are 5,000 ft higher, the range will be 87 nm. Of course high terrain, interference from other transmitters on the same frequency, or a low-power transmitter can reduce that range significantly.

Reciprocal Heading

If known heading is 0 -180, add 200 and substract 20. If known heading is 181 - 360, substract 200 and add 20. This is easier and quicker than trying to add or substract 180. EX: Reciprocal of 120 is 120 + 200 = 320, 320 - 20 =300.
EX: Reciprocal of 210 is 210 - 200 = 10, 10 + 20 = 30

Northerly Turning Error:

Another easy way to remember this compass tendancy is:
Accelerate - North, Decelerate - South.

Partial Panel
If every 30degress takes 10 seconds, then anytime you have the big numbers on the DG, such as 030, 060, 090, the time in between each will be 10 seconds.

In order to also help you, if you think that you have to turn to a heading that is LOWER usualy turn LEFT.

I know that this does not work if you are on a NW heading and have to go to a north east heading, but use common sense.

IFR approach or hold.

Time, turn, throttles, twist, track, talk

Time: start timing as required
Turn: start turning to the desired course
Throttles: set as applicable, precision approach, holding, etc
Twist: re-set the HSI inbound course window if required
Track: fly the airplane and track the inbound course
Talk: tell the controller if you need to.

Calculating VDP
VDP - A point along a straight-in approach at which a 3 degree slope to the runway cannot be maintained resulting in a, missed approach, circle to land,or unsafe manuever.
VDP’s are for straight in approaches and are simply used for a will indicate to you that a 3 degree descent path to the runway will not be obtainable from that position without an evasive manuever
There are three ways to calculate VDP:
1. They are published on the approach plate.
2. By DME - 300ft per nautical mile (from end of the runway)
EX. Say the MDA = 600 and the runway is 1 DME from the fix VOR, LOC, NDB, ETC) Your VDP = 3 DME 600/300 = 2 DME plus the 1 DME = 3 DME
3. Take 10% HAT off your time.
EX. Say the published HAT is 800ft and the time for that approach is 5:20 Your VDP will be at 4:00 along the approach. 10% of 800 = 80 seconds, subtract that from 5:20 and you get 4:00

Partial Panel Compass Flying
"OSUN" used for partial panel compass flying.
O vershoot S outh U ndershoot N orth
Remember that the magnetic compass lags from the North and leads to the south. How much you over or under shoot your desired heading depends on the degrees latitude that you are flying. Overshoot the South heading by the required degrees and Undershoot the North heading by the required degrees.
Ex.1 Suppose you are flying in Kansas (approximately 30 degrees latitude) and your heading is 090 degrees and you want to turn to a North heading. Because of the lags to the North you should roll out of your turn when your com pass reads 330 (360- 30=330 degrees)if your turn is to the right and 030 (360+30=030 degrees) if your turn is to the left.
Ex.2 Suppose you are still flying in Kansas and your heading is still 090 and you want to make a turn to a south h eading. Because the compass leads to the South you should roll out of your turn when your compass reads 210 (180+30=210 degrees) if the turn is to the right and 150 (180-30=150 degrees) if your turn is to the left

H. holding entry
M. missed approaches
T. TAS changes by 5% or 10 knots
L. loss of navigation equipment, VOR / DME etc.
C. cumpulsory reporting points
W. when unable to climb or descend 500 feet per minute

D. deviating for weather
V. vacating altitude

E. ETA changes

30 Day VOR Check
Required Items to record for VOR check: SLED: S-signature, L-location, E-error, D-date
5 A's
ATIS, ALTIMETER, AVIONICS, APPROACH BRIEF, AIRCRAFT. Atis: record atis or awos for weather, Altimeter: set current altimeter, Avionics: set comms, approach brief: make sure your landing at the right airport, aircraft: go threw the inrange/descent checklist
6 T's
Use for entry into holding: Time - note time (for reporting entry into holding); Turn - turn to outbound heading; Time - start timing outbound; Transition - slow to holding speed; Twistercept - twist OBS to inbound course and then intercept it; Talk - report established in holding
A - ATIS, M - Minimums, O - Overshoot, R - Radio setup, T - Timing, E - Emergencies
Approach Setup
 W= Weather (ATIS/AWOS), I= Instruments (HSI), S= Stack (Radios), P= Procedure (Courses)
Brief the approach
Atis, Markers/ magnetic deviation, Ident, Course, Enrty, Alt, Time, Missed instructions
Calculating VDP
VDP - A point along a straight-in approach at which a 3 degree slope to the runway can not be maintained resulting in a VDP’s are for straight in approaches and are simply used for a will indicate to you that a 3 degree descent path to the runway will not be obtainable from that position without an evasive manuever. There are three ways to calculate VDP: 1. They are published on the approach plate. 2. By DME - 300ft per nautical mile (from end of the runway) EX. Say the MDA = 600 and the runway is 1 DME from the fix VOR. 3. Take 10% HAT off your time. EX. Say the published HAT is 800ft and the time for that approach is 5:20 Your VDP will be at 4:00 along the approach. 10% of 800 = 80 seconds
CRAFT: Cleared, Route, Alt, Freq, Transponder. Ex: C: cleared as filed, R: right hdg 220, A: 4000 exp 1000 - 10 min after, F: 126.9, T: 2065
Heading to fly on Teardrop Entry
To help remember whether to add or subract 30 from the outbound heading in determining the correct teardrop heading. Holding on the 360 radial with left turns- add 30 to arrive at 030. Holding on the 360 radial with right turns- subtract 30 to arrive at 330

If your holding radial is opposite the direction of flight, your entry will be direct. If your holding radial is about the same as your heading, your entry will be either teardrop or parallel. 

Approach Briefing

1.       Identify Procedure and date

2.       Final approach nav aid tuned and ID'd

3.       Inbound course verified & set in #1 CDI/HSI

4.       Final approach fix ALT ______

5.       GS crossing ALT _____

6.       Missed-approach point marked

7.       DA is at what ALT ________ and minimal visibility is _______ distance

8.       Time for approach is ______

9.       Missed approach procedure is ___________

10.    No Flags

11.    Passengers secured

12.    Flaps

13.    Power

14.    Gear

Missed Approach

1.       Pitch-up

2.       Power-up

3.       Flaps Initial

4.       Positive Rate of climb

5.       Gear Up

6.       Turn to missed course

7.       Flaps up


8.       Advise tower of missed approach

Stark 1, 2, 3

But like other pilots, if Stark tried to turn in the clouds, he would quickly lose control. Wisely, he conducted his experiments at altitude, with plenty of clear air between the bases of clouds and the surface in which to recover from the steep spirals he'd invariably find himself in. Then Stark had an epiphany -- "blind" flying requires a pilot to ignore his/her veiled sensations of movement that quickly lead to vertigo, and instead trust the instruments to reflect true motion. Using instrument cues, Stark devised a means of recovering from unusual flight attitudes:

  1. Stop the turn (with rudder pressure based on the turn needle indication);
  2. Level the wings (by centering the slip/skid ball with the turn stopped); and
  3. Control the airspeed (with careful application of elevator based on the airspeed indicator's trend)

If what he called the "Stark 1, 2, 3 System" worked to recover from a loss of control, Stark concluded, it could be used to anticipate control loss and therefore permit prolonged instrument flight without losing control in the first place. He soon found his theory worked.

Stark and his wife penned a pamphlet describing the Stark 1, 2, 3 System and sold it by mail. He instructed other Colonial Airways pilots in the technique. Word spread quickly and soon airlines across the U.S. and in Europe were using Stark's technique, several hiring Stark to personally teach it to their pilots. Charles Lindbergh credited Stark in making his trans-Atlantic flight possible.

It was only a few years before Sperry developed gyroscopic attitude and heading indicators, making modern instrument flight possible -- but it was Howard Stark who taught the world to fly in IMC. Stark died on a transcontinental flight, but not from loss of control. He was forced down in the mountains in a heavy snowstorm, and froze to death trying to walk out.

More modern AIs are much less likely to tumble, but they are not immune from the hazard. In a rapid rate of pitch, bank and/or yaw change it's possible even a brand-new AI may become unusable in an unusual attitude recovery. Following the AI in an extreme nose-up or -down attitude, especially with a steep bank, might make matters even worse if the AI begins to tumble in the maneuver. The errant horizon line will provide no inkling it's failed.

That's one reason why most instructors teach unusual attitude recoveries by reference to instruments other than the attitude indicator. (The main reason is that a failed AI is probably the most likely reason an instrument-rated pilot would find him/herself in an unusual attitude in the first place). In anything other than the mildest of attitude excursions, it's best to regain control using the "partial panel" references of rate of turn, airspeed and altimeter, then cross-check the AI once under control to confirm whether it's still providing truthful information.

Turn and Bank vs. Turn Coordinator

Turn-and-slip indicator, and turn coordinator. (From the Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25.)

Sperry's original gyroscopic Turn Indicator eventually developed into two types of instruments: the turn & bank (T&B, or "turn needle") and the later turn coordinator (TC). Both incorporate a gravity "ball" slip/skid indicator, or inclinometer, to indicate the "quality" of the turn. Many pilots feel the T&B provides a more obvious indication of rate of turn, while rate-based autopilot systems require a TC in order to function.

TCs look something like an attitude indicator and sometimes there's confusion about what they really show, so much so that many TCs have the words "No Pitch Information" written right on the face of the instrument. "Glass cockpit" airplanes that include a rate-based autopilot like the KAP140 or the S-TEC line still require the TC, but may hide it behind the instrument panel, out of view.

Whether it's a T&B or a TC, however, the different mounting of the rate-of-turn's drive gyroscope (compared to an attitude indicator's required orientation) make the rate-of-turn immune to tumbling in unusual attitudes. Nose high or nose low, wings level or steeply banked, you can trust your rate-of-turn to help get you back under control. Proper recovery from unusual attitudes is less a question of which type of rate-of-turn indicator the airplane has than it is the pilot's training and currency using the rate instrument in unusual attitude recoveries.

Back-Up AIs

FAA Advisory Circular 91-75 authorizes replacing a T&B or TC with a back-up attitude indicator, subject to some rules about redundant power supplies and retaining a requirement for a slip/skid indicator (inclinometer) in the primary instrument scan. The backup AI is generally considered an improvement over the original rate-of-turn indicators, and it's easier to fly precisely using a backup attitude indicator than "traditional" partial-panel techniques should the primary AI or its drive system fail.

Given the tendency of AIs to tumble in unusual attitudes, though, and for pilots who don't own the airplanes they fly (and have no say in how they are equipped), it might be a good investment to train to proficiency on unusual attitude recoveries using the T&B or TC and the Stark 1, 2, 3 method. In fact, installing a small turn and bank instrument near the primary flight display (PFD) of a glass cockpit airplane, or moving a hidden turn coordinator from behind the panel to a spot in full view in airplanes with rate-based autopilots, might look like a step backward in panel design but would add a much-needed level of redundancy in the event of a PFD failure.

No matter what indicators you use, remember the key to recovering from unusual flight attitudes:

  1. Stop the turn;
  2. Level the wings;
  3. Control the airspeed

It's as easy as Stark's 1, 2, 3.

Fly safe, and have fun!

Stabilized descent with compass only

Gently turn aircraft to East or West heading. Trim aircraft to VA or best glide. Adjust power to establish a 200’ to 500’ per minute descent rate. Remove hands from control wheel or stick. Use rudder pressure to hold the cardinal East or West heading. Focus on maintaining heading with a minimum of rudder control as the compass is very unstable. This descent can be utilized in smooth air with loss of all gyros. I have demonstrated to this technique to many students and practiced it myself and had success under the hood (foggles) in letting down in a stabilized fashion without visual cues or gyroscopic instruments.

Holding, mental heading and timing computations

                As for drift correction the old rule is to double or triple your inbound correction on the outbound leg.

                However another method is delineated below. Also, the inbound leg being 1 minute, should be adjusted on

                the outbound leg. For example, add one second per knot of headwind and subtract for a tailwind.


Holding axis 030 degrees

Wind 240 degrees at 20 knots

TAS 90 kts, max drift is 14 degrees

Wind angle is 30 degrees. Compare to 60 and take half off.

Drift inbound is therefore 7 degrees (14 max drift x ½)

Heading outbound is 210 plus 21 which equals 231 degrees (7 degrees x 3)

(90- WA) = 60; Use the full headwind of 20 knots.

Go outbound for 1 minute 20 seconds (1 sec for each 1 knot)

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