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13 Answers

Go-around procedure

Asked by: 9460 views Aerodynamics, Commercial Pilot

Hello all,

I wanted some advice on a procedural-type question. In the PA-44 (Piper Seminole) go around procedure, it is listed as follows:

  • MIXTURES ............................................FULL RICH
  • PROPELLERS ............................................ FULL INCREASE THROTTLES.............................................FULL OPEN
  • Control Wheel...........................BACK PRESSURE TO OBTAIN POSITIVE CLIMB ATTITUDE
  • FLAPS....................................................RETRACT SLOWLY
  • GEAR .........................................................................UP
  • COWL FLAPS........................................................... AS REQUIRED

(You can find this on any online version of the PA-44 PIM - here's a link to an example on page 4-17)

Now, the way I have always been taught is to go full throttle, carb heat off (not listed in PIM), flaps 40°->25° immediately, then 25°->10° at positive rate, and 10°->0° upon being above Vy, then gear up, and cowl flaps open.

I began researching the Airplane Flying Handbook and it states in the Transition to Multi-Engines section (page 12-18) that, "With sufficient airspeed, the flaps should be retracted from full to an intermediate position and the landing gear retracted when there is a positive rate of climb and no chance of runway contact. The remaining flaps should then be retracted. [Figure 12-10]"

My question is this: would a better go-around procedure be full throttle, carb heat off, bring the flaps to 25°, then gear up, then continue as previously specified? This would reduce the drag the gear is giving a lot sooner, briefly take advantage of the increased lift coefficient 25° degrees of flaps gives (that is the specified flap setting for the short field take-off), and also follow the AFH procedure.

Thoughts?

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13 Answers



  1. Warren Webb Jr on Dec 29, 2018

    The proper procedure is to follow the POH, which you listed above. It is developed by the airplane’s engineers and test pilots and is what should work best for this model. The Airplane Flying Handbook includes a comment on page 12-2 that the POH takes precedence.

    Your point about the gear is a good one and I congratulate you for your analysis. The critical factors would be the power available, drag produced by the flaps, and drag produced by the gear, which in some models is different during retraction compared to drag in the down and locked position. Presumably the manufacturer thoroughly tested different sequences in retracting flaps and gear, and figured out what is best for this model.

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  2. John D Collins on Dec 30, 2018

    I don’t see a conflict with the POH procedure and the more detailed version you suggest. The POH procedures are not mandatory and in this case lack a lot of specificity. The procedures in section 4, Normal operations are guidance. In the case of section 2 of the POH, limitations, these are regulatory and are required to be complied with.

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  3. Warren Webb Jr on Dec 30, 2018

    Keep in mind the ACS includes these two expectations on go-arounds: The applicant demonstrates the ability to “Complete the appropriate checklist” and “Configure the airplane after a positive rate of climb has been verified or in accordance with airplane manufacturer’s instructions”. So you might want to have a conversation with the Examiner.

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  4. Kris Kortokrax on Dec 30, 2018

    We need to think about what we are doing, rather than being mechanical.

    Carb heat OFF is not mentioned in the go around procedure because Carb hear ON is not specified in the before landing checklist. Remove that from your list.

    Have you ever done a drag demo with the airplane to determine what produces the most drag?

    The Airplane Flying Handbook suggests retracting from full flaps to an intermediate setting. Usually full flaps will create the most drag (not considering a windmilling prop here).

    Once you have reduced that drag, you want to see a positive rate of climb before retracting the gear. This is because it is much more desirable to have the wheels contact the runway, as opposed to the belly of the airplane, if it sags. Get away from the runway a bit, then retract the gear.

    By now, you should be somewhere near best rate of climb speed. Go ahead and retract the rest of the flaps.

    It doesn’t look like Piper put a whole lot of thought into this part of the checklist. All they ask is to set an attitude for positive rate of climb before beginning to retract flaps and gear. It would make more sense to assure that you have actually achieved a positive rate of climb prior to retraction.

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  5. Warren Webb Jr on Dec 31, 2018

    The drag analysis Kris mentioned is the only way you will know. In the POH expanded section 4, there’s a good discussion on use of flaps on takeoffs which would be related to performance on a go-around. It can be debated both ways, but the manufacturer strongly favors no flaps for takeoffs to maintain the best safety margin so the go-around procedure may have resulted with that in mind also. I looked at the go-around checklists for the Seneca and Baron and they both have flap retraction before gear retraction.

    The Airplane Flying Handbook is the bible, but, it doesn’t apply 100% of the time. An example is the generally recommended approach speed of 1.3 times Vso. That is wildly off the recommended approach speed for the C172P. (Vso 33 x 1.3 = 43. Recommended short-field approach speed 61). Let’s us know what you find.

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  6. Kris Kortokrax on Dec 31, 2018

    The laws of physics don’t vary wildly.
    You just have to use the right numbers in the equation.

    For doing airspeed calculations, we use calibrated airspeed, not indicated airspeed.

    On page 5-12 of my Cessna 172P manual, it shows calibrated airspeed of 46 K for full flaps and 51 K for flaps up.

    1.3 X 46 = 59.8 KCAS
    1.3 X 51 = 66.3 KCAS

    Using the airspeed calibration table on page 5-9, this would yield 60.8 KIAS as Vref with full flaps and 67.3 KIAS as Vref with flaps up.

    These are very close to the lower end of the range of airspeeds listed on page 4-10 (65-75 KIAS flaps up), (60-70 KIAS full flaps).

    Rounding 60.8 up gives 61 KIAS (exactly the speed listed for short field landing).

    It is also important to realize that the speeds quoted are for an airplane at gross weight. The stall speed goes down at the ratio of the square root of the present weight divided by the max gross weight.

    If our example airplane weighed 2100 pounds instead of 2400 pounds, then 2100 / 2400 = .875. The square root of .875 is .935.

    46 KCAS X .935 = 43 KCAS
    43 X 1.3 = 56 KCAS
    56 KCAS would be about 53 KIAS for Vref at 2100#.

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  7. Warren Webb Jr on Dec 31, 2018

    Kris – very interesting lesson – thank you for that. I can understand where engineers would have to use calibrated airspeeds. However, as stated in the Pilot’s Handbook of Aeronautical Knowledge, manufacturers use indicated airspeed for takeoff, landing, and stall speeds and airspeed regulations for maximum airspeeds (ex below 10,000ft) use indicated airspeed. I don’t think the FAA expects pilots to get into any time-consuming math equations while flying the airplane. In the case of a C172P approach, the FAA Handbook indicates the POH takes precedence which as you know has 61 knots indicated airspeed as the correct airspeed. 1.3 x Vso (which is an indicated airspeed and is their formula) comes to 43, a lot different than 61. Are we on the same page? I’m not even sure. Thanks – have a great New Year’s.

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  8. Kris Kortokrax on Jan 02, 2019

    There is a difference between determining airspeeds for design and calculation purposes (CAS) and determining airspeeds to display on airspeed indicators (IAS).

    14 CFR 23.49 (which no longer exists, but did exist when the 172 and most other airplanes were certified) specifically states that Vso and Vs1 are determined in KCAS.

    AC 23-8C, which deals with flight testing Part 23 airplanes requires that stall speeds be determined in IAS for display on the airspeed indicator and CAS for all other purposes.

    While the FAA might not want pilots to perform calculations during flight, that does not mean that the FAA ignores time consuming calculations. It requires calculations for flight planning and weight & balance. These are normally done prior to flight (albeit nowadays by an iPad). If one is considering landing on a short runway, it would seem that the time spent on the ground to determine Vref at the landing weight would be well worth the effort. If one is landing a C172 on a 7000′ concrete runway, it is not as critical.

    The POH does not need to take precedence for me, because the Vref that I calculated using calibrated airspeed exactly matches the POH.

    Vso, by definition in 23.49, is a calibrated airspeed. You will not find anywhere, a formula explicitly stating that Vref calculations are based on indicated airspeed.

    This information is not something that I derived myself. It is information that I learned from Bill Kershner’s Advanced Pilot’s Flight Manual. I bought the book when I started flight instructing 30 years ago to set a baseline for what I would teach my students. The calculation using calibrated airspeed is repeatable for any airplane and the numbers derived are in agreement with the recommendations published in various POHs.

    We are definitely not on the same page and won’t ever be, as long as you cling to the idea that indicated airspeed can be used in Vref calculations.

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  9. Warren Webb Jr on Jan 04, 2019

    Kris – I did the calculations on a C152, C172, and a SR22 for a comparison, since the Cessna Vso’s had a CAS higher than IAS and the Cirrus Vso had a CAS lower than IAS. The recommended IAS brought each CAS to very nearly the Vso x 1.3 in each case, just as you said. Thanks.
    C152 Vso CAS 43 x 1.3 = 55.9. Recommended approach speed 54 IAS = 55 CAS.
    C172 Vso CAS 48 x 1.3 = 62.4. Recommended approach speed 61 IAS = 64 CAS.
    SR22 Vso CAS 59 x 1.3 = 76.7. Recommended approach speed 77 IAS = 77 CAS.

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  10. Warren Webb Jr on Jan 05, 2019

    C172 is C172S model.

    C152 Vso CAS 43 x 1.3 = 55.9. Recommended approach speed 54 IAS = 55 CAS.
    C172S Vso CAS 48 x 1.3 = 62.4. Recommended approach speed 61 IAS = 64 CAS.
    SR22 Vso CAS 59 x 1.3 = 76.7. Recommended approach speed 77 IAS = 77 CAS.

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  11. Warren Webb Jr on Jan 05, 2019

    Kris – could you explain your conversion of 59.8 KCAS to 60.8 KIAS? The POH I see online has 61 KCAS = 60 KIAS, 53 KCAS = 50 KIAS. I’m getting 58.5 KIAS.

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  12. Kris Kortokrax on Jan 07, 2019

    Must have been looking at it early in the morning. It should go the other way to 58.8, instead of 60.8. I reversed the numbers.

    Now find me a pilot who can hold that exact airspeed for the time it takes to fly down final on a short field approach. Private ACS tolerance is +10/-5.

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  13. Brian on Apr 16, 2019

    Kris is spot on. Calibrated speeds should be used for calculations and then converted to indicated for use in flight. Taking that one step further, if the operating handbook doesn’t offer altitude/temp (hard to find ones that don’t these days) then you convert calibrated to true for the calculation. Finally, above 10 you’ll convert that to equivalent to account for compressibility. This is what both part 23 and part 25 do for you in the charts they create.

    If it helps, remember that indicated airspeed is “calibrated airspeed corrected for instrument and installation errors.” In other words, it is an inaccurate speed for calculation.

    Also I saw you comparing pipers to cessnas with your vref calculations. Cessnas speeds are far more erroneous because the pitot tube is placed in front of the flaps. Extending the flaps angles the relative wind forward of the flap down, striking the pitot at a sharper angle and creating the large difference in celebrates vs indicated speeds you see in many Cessna aircraft. The Fowler design of the 172 compounds this. Piper, on the other hand, places the pitot outboard and away from the flaps. As a result you see a lesser difference between calibrated and indicated speeds across the full configuration range of the aircraft. Cirus is similarly designed and it’s plain flap design is less impactful to flow as well, a necessity for its smoother wing design.

    Anyway! The point here was listen to Kris. Using indicated speeds are correct for flight. Using them to calculate is akin to making up moment arms for a w&b calculation. Calculate with CAS. Convert it to IAS for flight.

    Safe flying ladies and gents! Glad to see these spirited discussions still go on in my abscents!

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