Curious as to how everyone manages flaps in Short/Soft field take offs and short field landings. I realize every plane is different and some planes, such as Cirrus, have defined flap settings even for normal takeoffs while others, such as the Grumman AA-5 I flew actually recommend against full flap landings so for the purpose of this conversation, I am particularly interested in flap management of typical trainers, particularly C172's (and like) and PA28's (and like) aircraft.
I recently got into a discussion with a CFI about what the book says about short/soft field takeoffs, what the FAA in the form of a DPE says and how they differ from what was being taught.
The handbook says to retract flaps at a safe maneuvering altitude.
The DPE says the FAA likes to see the flaps retracted at 700 AGL.
The CFI says the flaps should be retracted as soon as you clear the obstacle and put forward that teaching students to retract them higher is bad form since the FAA (via the book, whether the DPE as a designate representative of the FAA is the FAA or not is another debate) doesn't say to retract them at 700 AGL.
To me, I find the book and the DPE to be closer to in-sync than the CFI on the basis that the first 2 notches of flap are generating more lift than they are drag so early retraction of flaps reduces lift and can cause you to settle back into your obstacle(s) (lets assume its a forest of 50' trees).
Additionally, looking at the "safe maneuvering altitude" I could make the argument that, independent of the DPE's comments, the recommendation by the FAA to wait to turn cross wind until 700 ft AGL and limiting turns before this point to the minimum necessary shallow turns to comply with any obstacle avoidance or noise abatement procedure is indication that 700 AGL is the point that the FAA considers to be the safe maneuvering altitude. Conversely, while it deals with approaches not departures I could also make the argument that flaps should not be retracted before 400 ft AGL on the basis that stabilized approach criteria says you should minimize changes to the aircraft configuration during the critical stage of the approach below 400ft AGL and should reject a landing that is not stable by this point, meaning the FAA considers anything above 400ft AGL to be safe maneuvering territory. In other words, flaps should not be touched until at least 400ft AGL and since I advocate not to change flaps in a turn (while flaps are manual in the PA28, they are motorized in the C172 and other aircraft and I would not want for 1 of 2 flap motors to burn out unexpectedly leaving me with split flaps while in a turn) at or before 700 ft AGL since that is the point at which you should be turning Xwind.
Secondary to the takeoff question I have a similar question for shortfield landings...
When I learned in a Cessna, I was told to leave flaps in after touch down for the aerodynamic braking since they produce more drag than lift at higher settings (especially true in Cessna's with a 4 notch flap setting going to 40-degrees, notably the notch 3 setting on a PA28).
The book doesn't really say though it does say to use max aerodynamic braking and at flaps 3/40-degrees in a PA-28, they similarly generate more drag than lift for the given configuration.
Ive noticed that instructors at my last 2 flight schools (in separate geographically disperse states so its not a single regional data point that can be ignored) have been suggesting to remove flaps almost immediately after landing so that the planes weight can settle on the wheels and max braking applied.
Much like the retracting of flaps on takeoff, I have 4 issues with this guidance issued:
1) The handbook specifically says to use aerodynamic braking until weight has settled on to the main wheels before applying the brakes. It does not say I should quicken this process by changing flap settings. The Piper PA28 POH does not have a procedure listed for shortfield landings.
2) While its fairly easy to dump all of the flaps in a PA28 rapidly, in other aircraft (again such as a cessna) there is at least a few moments where the flaps are in motion changing the lift/drag profile of the aircraft. Therefore, even if I immediately reach across and go flaps 0, there is a delay between doing that and the flaps no longer affecting airflow over the wing during which the flaps will briefly produce more lift than drag having an opposite affect to the one desired (lightening the load on the wheels initially)
3) I look at the procedure for a short-field takeoff and note that it requires 2 notches of flaps... If I had a sudden runway incursion on a short field landing or judged that my ground roll would be long or had other reason to abort the landing after touchdown and I had retracted the flaps, I am no longer generating that extra lift that a short-field is said to need. I am also already going to be at an airspeed low enough that lift is no longer sufficient to keep the airplane in the air (hence the need for minimum flare), retracting the flaps is only going to serve to increase the airspeed I need to make that aborted landing into a successful go-around which may not be possible with the remaining runway left.
4) The ground roll is still a critical phase of flight in my mind. Sure its less dangerous than when you are low and slow but you still need to maintain the runway and avoid crashing into anything that might enter the runway while slowing down yet still be ready to jam that power in and take off again if the situation requires it. It also becomes even more critical if the reason for the "short field" is a LAHSO clearance... I know which one will win if the decision comes down to fiddling with the flap position vs maintaining awareness of the LAHSO stop point and not entering the runway on which an airplane is about to takeoff or land. I also note that there are many CFIs, DPEs and other pilots who seem to think similarly about ground roll as they generally feel you should wait until you are clear of the runway before doing any part of the after landing checklist and cleaning up the aircraft. It makes sense that there is an exception in there for TNG's or Stop-n-goes given you are immediately taking flight again but it makes less sense for a short-field landing where you presumably dont have enough runway and should not be conducting such operations preferring instead to taxi back.
My arguments for/against flap retraction notwithstanding, the principle of primacy and all of that, I've found it difficult to appease my instructors and remember to retract the flaps immediately on touch down and either my CPL DPE didnt notice (unlikely), didnt feel the need to comment or felt my procedure was correct, I did not remove the flaps immediately on my CPL checkride and still passed but I want to make sure I do it right on my CFI checkride and I dont create a new primacy in a new student that is wrong or even if there is a lack of consensus, at least cant be defended with sound reasoning.
I recently got into a discussion with a CFI about what the book says about short/soft field takeoffs, what the FAA in the form of a DPE says and how they differ from what was being taught.
The handbook says to retract flaps at a safe maneuvering altitude.
The DPE says the FAA likes to see the flaps retracted at 700 AGL.
The CFI says the flaps should be retracted as soon as you clear the obstacle and put forward that teaching students to retract them higher is bad form since the FAA (via the book, whether the DPE as a designate representative of the FAA is the FAA or not is another debate) doesn't say to retract them at 700 AGL.
To me, I find the book and the DPE to be closer to in-sync than the CFI on the basis that the first 2 notches of flap are generating more lift than they are drag so early retraction of flaps reduces lift and can cause you to settle back into your obstacle(s) (lets assume its a forest of 50' trees).
Additionally, looking at the "safe maneuvering altitude" I could make the argument that, independent of the DPE's comments, the recommendation by the FAA to wait to turn cross wind until 700 ft AGL and limiting turns before this point to the minimum necessary shallow turns to comply with any obstacle avoidance or noise abatement procedure is indication that 700 AGL is the point that the FAA considers to be the safe maneuvering altitude. Conversely, while it deals with approaches not departures I could also make the argument that flaps should not be retracted before 400 ft AGL on the basis that stabilized approach criteria says you should minimize changes to the aircraft configuration during the critical stage of the approach below 400ft AGL and should reject a landing that is not stable by this point, meaning the FAA considers anything above 400ft AGL to be safe maneuvering territory. In other words, flaps should not be touched until at least 400ft AGL and since I advocate not to change flaps in a turn (while flaps are manual in the PA28, they are motorized in the C172 and other aircraft and I would not want for 1 of 2 flap motors to burn out unexpectedly leaving me with split flaps while in a turn) at or before 700 ft AGL since that is the point at which you should be turning Xwind.
Secondary to the takeoff question I have a similar question for shortfield landings...
When I learned in a Cessna, I was told to leave flaps in after touch down for the aerodynamic braking since they produce more drag than lift at higher settings (especially true in Cessna's with a 4 notch flap setting going to 40-degrees, notably the notch 3 setting on a PA28).
The book doesn't really say though it does say to use max aerodynamic braking and at flaps 3/40-degrees in a PA-28, they similarly generate more drag than lift for the given configuration.
Ive noticed that instructors at my last 2 flight schools (in separate geographically disperse states so its not a single regional data point that can be ignored) have been suggesting to remove flaps almost immediately after landing so that the planes weight can settle on the wheels and max braking applied.
Much like the retracting of flaps on takeoff, I have 4 issues with this guidance issued:
1) The handbook specifically says to use aerodynamic braking until weight has settled on to the main wheels before applying the brakes. It does not say I should quicken this process by changing flap settings. The Piper PA28 POH does not have a procedure listed for shortfield landings.
2) While its fairly easy to dump all of the flaps in a PA28 rapidly, in other aircraft (again such as a cessna) there is at least a few moments where the flaps are in motion changing the lift/drag profile of the aircraft. Therefore, even if I immediately reach across and go flaps 0, there is a delay between doing that and the flaps no longer affecting airflow over the wing during which the flaps will briefly produce more lift than drag having an opposite affect to the one desired (lightening the load on the wheels initially)
3) I look at the procedure for a short-field takeoff and note that it requires 2 notches of flaps... If I had a sudden runway incursion on a short field landing or judged that my ground roll would be long or had other reason to abort the landing after touchdown and I had retracted the flaps, I am no longer generating that extra lift that a short-field is said to need. I am also already going to be at an airspeed low enough that lift is no longer sufficient to keep the airplane in the air (hence the need for minimum flare), retracting the flaps is only going to serve to increase the airspeed I need to make that aborted landing into a successful go-around which may not be possible with the remaining runway left.
4) The ground roll is still a critical phase of flight in my mind. Sure its less dangerous than when you are low and slow but you still need to maintain the runway and avoid crashing into anything that might enter the runway while slowing down yet still be ready to jam that power in and take off again if the situation requires it. It also becomes even more critical if the reason for the "short field" is a LAHSO clearance... I know which one will win if the decision comes down to fiddling with the flap position vs maintaining awareness of the LAHSO stop point and not entering the runway on which an airplane is about to takeoff or land. I also note that there are many CFIs, DPEs and other pilots who seem to think similarly about ground roll as they generally feel you should wait until you are clear of the runway before doing any part of the after landing checklist and cleaning up the aircraft. It makes sense that there is an exception in there for TNG's or Stop-n-goes given you are immediately taking flight again but it makes less sense for a short-field landing where you presumably dont have enough runway and should not be conducting such operations preferring instead to taxi back.
My arguments for/against flap retraction notwithstanding, the principle of primacy and all of that, I've found it difficult to appease my instructors and remember to retract the flaps immediately on touch down and either my CPL DPE didnt notice (unlikely), didnt feel the need to comment or felt my procedure was correct, I did not remove the flaps immediately on my CPL checkride and still passed but I want to make sure I do it right on my CFI checkride and I dont create a new primacy in a new student that is wrong or even if there is a lack of consensus, at least cant be defended with sound reasoning.
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