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Checked Out From The SAFE Members Only Resource Center Society of Aviation and Flight Educators – www.safepilots.org. Aviation Rules of Thumb. John Mahany, ATP/MCFI Flight Advisor, EAA Chapter 7 FAASTeam Lead Rep, KLGB September 13, 2011. ATA SmartBrief, 8/30/11.

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Aviation rules of thumb

Checked Out From The SAFE Members Only Resource Center

Society of Aviation and Flight Educators – www.safepilots.org

Aviation Rules of Thumb

John Mahany, ATP/MCFI

Flight Advisor, EAA Chapter 7

FAASTeam Lead Rep, KLGB

September 13, 2011

Ata smartbrief 8 30 11

ATA SmartBrief, 8/30/11

  • Automation prompts safety officials' concern about pilots' skillsAirplanes are become increasingly automated, leading some safety officials to raise concerns that pilots might be losing their in-flight instincts, which could be troublesome when faced with an issue. Rory Kay, co-chairman of the Federal Aviation Administration's committee on pilot training and an airline captain, says that the industry is suffering from "automation addiction," which is leading to different types of incidents.

Ata smartbrief cont

ATA SmartBrief, cont.

  • "We think the best way to handle this is through the policies and training of the airlines to ensure they stipulate that the pilots devote a fair amount of time to manually flying," said Paul Railsback, operations director at the Air Transport Association. "We want to encourage pilots to do that and not rely 100% on the automation. I think many airlines are moving in that direction."

More on piloting skills

More on piloting skills

  • The ability of pilots to respond to the unexpected loss or malfunction of automated aircraft systems "is the big issue that we can no longer hide from in aviation," said Bill Voss, president of the Flight Safety Foundation in Alexandria, Va. "We've been very slow to recognize the consequence of it and deal with it."

Some aviation rules of thumb

Some Aviation Rules of Thumb

  • Navigation reciprocals

  • Normally aspirated & Turbo-charged

  • Density Altitude

  • Takeoff Performance

  • Crosswind Component

  • Vx & Vy

  • Cruise Climb

More aviation rules of thumb

More Aviation Rules of Thumb

  • Flight Planning & ISA

  • Figuring TAS

  • Figuring Va

  • Engine Failure

  • Converting KTS to MPH

  • Maximum Glide

  • Icing, weather, descent planning…

  • Your own?

Navigation reciprocals

Navigation reciprocals

  • Take the 1st digit plus two, 2nd digit minus two; or visa versa;

    • Minus two, plus two

      • 180 becomes 360

      • 090 becomes 270

Related accident

Related accident?

  • Lexington, KY CRJ takeoff accident,

    • Aug. 27, 2006

    • Did they ‘brief’ the takeoff??

    • Were their ‘Heading Bugs’ properly set?

    • They did not realize they were on the wrong runway until it was too late, at rotation….

Comair 5191 cvr

Comair 5191 CVR

  • Pilot: Thrust SetPilot: That is weird, No LightsPilot: YeahPilot: 100 KnotsPilot: CheckPilot: vee onePilot: RotatePilot: Whoa!

Generic takeoff briefing

Generic Takeoff Briefing

  • Departing KSNA or any other; confirm R/W _ _

  • If applicable, r/w is _ _ _ _ ft. long

  • Density Altitude if applicable, is _ _ _ _

  • Takeoff weather/visibility is ‘X’; T/O alternate?

  • Up to Vr, will abort for _ _ _

  • Once airborne, if engine fails then _ _ _

  • Any noise, DP or terrain issues?

  • In event of emergency return, plan is ??

Normally aspirated engines

Normally aspirated engines

  • A normally aspirated engine – only produces rated Hp at Sea Level on a ‘Standard Day’, or ISA; 15C or 59F

  • It loses 3 ½ % - 4% hp for each 1000’ increase in altitude.

  • Every 10 deg. F/6C above ISA results in 1% less power output

Turbo charged engines

Turbo-Charged Engines

  • Takeoff fuel flow –

    • Your takeoff fuel flow should be at least 10%

    • of your max rated hp. ie., for 285hp, expect

    • 28.5 gph; 310hp should be at least 31.0gph

    • For turbo-normalized (8.5-1) it should be somewhat less

    • CHT during takeoff/climb should be < 380F

    • Source, Mike Busch, Savvy Aviator

Density altitude

Density Altitude

  • For every 10F above ISA, add 600’ to

    the airport elevation to figure density

    altitude and your airplanes performance.

    source, Richard L. Collins

Density altitude1

Density Altitude

  • From AOPA Safety Advisor #6,

    • Mastering Takeoffs and Landings

    • ‘the simple act of taking off or landing

    • accounts for 50% of all general aviation

    • related accidents’

Big bear city ca takeoff 6748 msl

Big Bear City, CA, takeoff - 6748’ msl

  • What is your density altitude?

  • What is your takeoff performance?

  • Do you know how to lean for takeoff?

    • Begin the takeoff roll, and with full power, lean the mixture until there is some roughnesss, then enrichen until it runs smoothly.

    • source, Mountain Flying Bible

Takeoff performance

Takeoff performance

  • T/O distance increases 15% for each 1000’

    • Increase in Density Altitude above S.L.

      A 10% change in aircraft weight will result in a

      20% change in the takeoff distance required

      source; Mountain Flying Bible

Takeoff flap setting

Takeoff flap setting

  • If you want to use flaps for takeoff, but there is no reference in the P.O.H., suggest turning the yoke full scale, either direction and lower the flaps to approximately match the down aileron deflection.

  • source, Mountain Flying Bible

Takeoff performance1

Takeoff performance

Short field takeoff advice from the late Sparky Imeson, noted mountain flying expert;

If you have not reached 70% of your takeoff speed ½ way down the runway, ABORT!

Also, make sure the parking brake is OFF! 

  • source, Mountain Flying Bible

Crosswind component

Crosswind component

  • The 5, 7, 9 rule

    • Runway numbers are magnetic; ATIS/ASOS

      winds are magnetic

    • If the wind is 30, 45 or 60 degrees to the R/W

      • Take 50, 70 or 90% of the wind velocity; this becomes the direct crosswind component.

      • Note; Crosswinds are not hard limits; they are only ‘demonstrated’; more importantly, how is your cross-wind proficiency?

Vx vy

Vx & Vy

  • Both Vx & Vy decrease 1 knot per

    100 pounds below max gross weight

    Verify this in the P.O.H.

Cruise climb speed

Cruise Climb speed

  • Vy – Vx = C. Add C to Vy, this is cruise climb

  • Ex., a CE 172S; Vy 74 knots; Vx 62; C = 12

    74 + 12 = 86 suggested for cruise climb.

    P.O.H. shows 70 – 85Kts for cruise climb

  • A more efficient climb. Better engine cooling with a lower, better deck angle. Source, Fly

    the Engine, Kas Thomas

Flt planning figuring isa

Flt. Planning - Figuring ISA

  • Int’l Standard Atmosphere…ISA

  • Found in the P.O.H. in performance charts

    • ISA is 59F or 15C at sea level, 29.92”hg

    • To find ISA at altitude; take cruise altitude, x 2, subtract 15, then change the sign (+/-)

    • 5,000’; 5 x 2 = 10 - 15 = -5; becomes +5.

    • 10,000’; 10 x 2 = 20 – 15 = +5; becomes -5

Figuring tas

Figuring TAS

  • How to find your approximate TAS

    • TAS increases approximately 2% per 1000’

    • What is your indicated altitude?

    • Double the 1st digit, and add to the IAS.

    • Result should approximate TAS

    • Example; 3000’, and 120 knots, TAS is ~ 3 x 2 = 6, 120 + 6 = 126 knots

The ice tea airspeed formula

The ‘ice tea’ airspeed formula

  • Airspeed relationships; how to remember

    The ‘iceT’ formula; indicated ~ calibrated, equivalent (applies to jets), True Airspeed. TAS increases with altitude. Indicated will decrease with altitude due to less dynamic pressure in the Pitot tube

Rule of 60

Rule of 60

  • At cruise TAS, each degree of crab angle

    x TAS multiple (60=1, 120=2, etc)

    = crosswind component

    Ie., @ 120 knots, each degree of crab is caused by a 2 degree x-wind component resulting in a ‘x’ degree drift correction.

    Ex., 5 degrees left x 2 = 10 knot cross wind

Maneuvering speed va

Maneuvering Speed Va

  • Maneuvering Speed; Va = ~ 1.7 x Vs1

  • Reduce Va by 10% for each 20% reduction in gross weight. Or, reduce by 1% for each 2% reduction in G.W.

  • Remember, you are always BELOW G.W. at cruise. You burned fuel on taxi, takeoff and climb.

  • All ‘V’ speeds are predicated on G.W., so adjust accordingly for best performance.

Engine failure a b c s

Engine failure A, B, C’s

  • Airspeed – best glide

  • Best place to land – straight ahead, to the side, or behind you?

  • AircraftControl – maintain control!

    • Know your emergency checklist!

Engine failure maximum glide

Engine Failure, Maximum Glide

  • Weight has no effect on max glide range

  • Weight does have an effect on glide speed

  • Reduce glide speed 5% for each 10% reduction in gross weight

  • With a headwind, increase glide speed by 50% of the headwind component. Glider

    pilots use this technique.

Converting kts to mph

Converting KTS to MPH

  • Add 15%, or multiply by 1.15

  • 100kts = 115mph



  • No aircraft is certified for CONTINUOUS flight in KNOWN icing conditions

  • Icing/deice certification is only for flight THROUGH icing. Ref. FAR 25 Appendix C, icing certification

  • Check your P.O.H.

  • From, Professional Pilot, 3rd. ed., John Lowery



  • A rough rule of thumb for avoiding/escaping icing conditions – but it varies each time

    • Climb in a cold front towards colder temps (away from ice); if temps in the bases of developing cumulus clouds is -12C or warmer…expect heavy icing

    • Descend in a warm front to warmer temps below

    • Sources, Severe Weather Flying, Dennis Newton

    • Weather Flying, Bob Buck

Weather trw rules

Weather/TRW rules…

  • Storms tend to be stronger when the cold frontal passage occurs in the afternoon or evening. This is because the air can get more unstable out ahead of the front (i.e. daytime heating).

Ifr standard rate turn bank angle

IFR Standard Rate Turn bank angle

  • Take 10% of the IAS and add 5.

Ground speed

Ground Speed

  • Rough estimate

    • Add or subtract all of the headwind or tailwind

    • Add or subtract ½ of a quartering head or tailwind

Calculating ground speed piston drivers

Calculating Ground Speed - piston drivers

  • Note the time to fly a distance; ie., 30NM

  • 30/15; 15x 4 = 60; 4 x 30 = 120

    • 15 min to fly 30NM. G.S. = 120kts.

      10 min to fly 25NM; 10x6=60; 6x25 = 150 kts

Ground speed check vlj drivers

Ground Speed Check - VLJ drivers

  • For faster aircraft (at least 250 kts.) there is another G.S. check

  • Note the distance travelled in 36 seconds on the DME and multiply by 100.

  • 36 seconds is 1% of an hour.

  • So, if you travel 3NM, ground speed is 300 kts.

How to plan descents

How to plan descents

  • Suggestion; altitude to lose times 2 (500 FPM for pax comfort), times ground speed in miles per minute (1,2, 3, etc.), this is how many miles you will cover descending…adjust as needed for wind and plan when to start down accordingly

Descent planning from the flight levels

Descent planning from the flight levels

  • Multiply cruise altitude ( thousands of feet) x approx. 3 (depending on the aircraft and winds) to determine the approximate start of descent.

  • To descend from FL 250; 25 x 3 = 75

  • Begin descent 75 NM out

Intercept the glideslope

Intercept the glideslope

  • At G.S. intercept, lower the nose exactly whatever the G/S angle is, as shown on the approach plate. Capture is automatic.

  • This is typically ~ 3 degrees.

  • source, Barry Schiff, Proficient Pilot

Flying the glideslope

Flying the glideslope

  • Determine the proper ILS descent rate

    • Standard ILS descent rate = 300’/NM.

    • Take IAS / 2, add a zero; this is your Rate of Descent; 100kts / 2 = 50, add a ‘0’ = 500 FPM. 120 kts = 600 FPM

      Or, use this to figure the altitude to be at a given distance from a runway…for a stabilized




  • Approx. 42% of G.A. accidents occur during approach and landing

    • If the runway is wet and ungrooved, the landing ground roll doubles

    • Crossing the runway threshold higher than 50 feet; landing distance increases ~ 200’ for every 10’ of excess height

    • Every 10 kts of excess speed increases landing distance 20%

Aviation rules of thumb


  • For each 1000’ above S.L., the takeoff run will increase ~ 12%



  • Rollout from a turn; lead your bank by ½ the bank angle

  • Most structural icing occurs between 0C - 10C

Your own

Your own

Rules of Thumb???

Thank you

Thank you!

  • j.mahany@charter.net

  • www.johnmahany.com

This presentation has been donated to the SAFE Resource Center for the personal use of SAFE Members. Permission for any other intended use must be coordinated directly with the author.

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