FLAP RETRACTION AFTER TAKEOFF

[jlunseth]

2 hours ago, Ricky_231 said:

I had the O2 bottle on my K taken out for a hydrostatic test and holy smokes - even with almost 50lbs of "ballast" in the baggage compartment, the first couple of take offs were very weird. Exactly what you're describing - the mains would pop off the ground and it took a brisk, firm pull of the yoke to get the plane pointing in the right direction (up). More trim definitely helped.

Blame it on Jack Napoli. He is the Mooney PPP instructor who taught me to put a little trim-up in for takeoff. Note, I said a little. Better to need a little back pressure on the yoke to complete the task rather than have the aircraft take nose-up overcontrol on its own. As I said, its a quarter, maybe a half inch above the "takeoff" line on my trim indicator.

[PeteMc]

My mechanic right after I bought the plane told me to set the trim to the nose-up end of the Take-Off trim window.  And to hold some extra back pressure as I add power and started the roll.  He wanted me to do it to reduce the wear on the nose gear.  (Also a K.)

[KLudwick]

I've given ~100 hours of Mooney dual this year and put another 50 on mine.  I have always used and taught the same technique: as soon as the gear is up in the wheels wells and you make a quick scan of the instruments, retract the flaps.  The quick scan of the instruments lets you ensure proper climb speed, directional control, etc, and prepare for the additional slight pitch change when you retract takeoff flaps.  For Johnson bar machines, in many cases the scan allows you to get back on proper speed and heading seeing as many owners let one or the other slip during gear retraction.  Cleaning the airplane up and capturing/maintaining your preferred climb speed sooner allows for better second and third segment climb rates as well.  

We all fly our machines a bit differently, which makes flying more fun (and creates good buzz and conversation on MooneySpace)!

[Will.iam]

A data point for the ones feeling sink and wondering if the plane is actually sinking or if it could be still climbing…

You can in fact feel way less than just sinking to feeling like you are falling and yet still have an airplane still be climbing. It’s the rate of deceleration that makes the feeling. 
Went on some vomit commit rides. The airplane was accelerated to 325 knots at 10,000 ft and then pulled up to 85d nose up. Then immediately push lightly forward on the yoke at this moment everything was floating and you felt like you were falling but we were very much still going up at a rate pegged by the vsi of greater than 6000ft/min+ we would touch 20,000ft as we passed through nose level and could have leveled off abit almost at stall speed but that would have only given 15seconds. Still pushing the nose over and bringing the thrust to idle we would continue to about the same nose low before having to start pulling back to level by 10,000ft. Total floating time of about 30 seconds. 

[carusoam]

Great insight Will.!

Thanks for sharing the details with a great example.

Best regards,

-a-

[N201MKTurbo]

I always retract the flaps before the takeoff roll. I’ve never experienced any sink.

In the rare occasion that I do use takeoff flaps, I’m never in a hurry to retract them. Wait till you have everything cleared and a couple of hundred feet of altitude.

[Warren]

I wait for 90 knots to retract flaps.  At that speed you have good control and the sink is minimal if at all.  I find this takes out all the judgement, estimating,...

1.  Lift off the runway and out of ground effect.

2.  Positive rate - gear up.

3.  90 knots - retract flaps.

[Hank]

Different procedures for different models. This is for my C:

[T. Peterson]

On 7/9/2021 at 12:53 PM, GeeBee said:

An accelerating airplane likely will not sink because the aerodynamic pressure is increasing faster than the loss of coefficient of lift.

We would do well to review the lift equation. L=Cl x q x S where CL is the coefficient of lift, q is the aerodynamic force and S is the wing area.

q is calculated as 1/2 x p x V2 where p is the air density and V is the velocity. Notice the velocity is squared so a little bit of acceleration goes a long ways towards negating the loss in lift from a drop in CL

This is why an accelerating airplane will not sink, but a non accelerating airplane will sink. The numbers do not lie unless you want to repeal the laws of aerodynamics.

I think that most of us are assuming an accelerating airplane. I at least would not consider raising the flaps unless my airplane was accelerating.

[Pinecone]

On 7/9/2021 at 3:10 AM, donkaye said:

So, gear up at 50' or no more runway to land on and flaps up no less that 300' (to account for sink when flaps are raised) or after I'm done with a takeoff turn (for added safety margin).  That's the way I teach it.

That is what I do and it makes me happy.   

One thing, I don't think there is actual sink when retracting the flaps, but a momentary reduction in the climb rate.   Like the Vomit Comet mentioned, if you are going up at 700 FPM, and it drops to 650 FPM, you will feel a bit light in the seat

[larrynimmo]

When I retract my flaps, my nose will point skyward…unless I adjust my trim down…

I don’t lose any height, in fact my rate of climb and speed increase significantly.

in my J , flaps enable a lower speed take-off, but in my honest opinion don’t help me climb over obstacle.

I am not an engineer or a test pilot

[Shadrach]

10 hours ago, Pinecone said:

That is what I do and it makes me happy.   

One thing, I don't think there is actual sink when retracting the flaps, but a momentary reduction in the climb rate.   Like the Vomit Comet mentioned, if you are going up at 700 FPM, and it drops to 650 FPM, you will feel a bit light in the seat

Agreed...There is no actual sink. I think the feeling is mostly from the change in pitch as the plane rocks the nose higher due to the change in wing chord and center of lift.  I've heard seasoned instructors refer to the "sink" that occurs when raising flaps.  I hope they are referring to "feeling" of sinking rather than thinking there are two split second reversals in vertical trajectory.  It should seem ridiculous to anyone that has thought it through. 

[Shadrach]

8 hours ago, larrynimmo said:

When I retract my flaps, my nose will point skyward…unless I adjust my trim down…

I don’t lose any height, in fact my rate of climb and speed increase significantly.

in my J , flaps enable a lower speed take-off, but in my honest opinion don’t help me climb over obstacle.

I am not an engineer or a test pilot

removing drag will do that!

[Shadrach]

18 hours ago, T. Peterson said:

I think that most of us are assuming an accelerating airplane. I at least would not consider raising the flaps unless my airplane was accelerating.

I can think of one scenario.  If I lost the engine after crossing abeam the numbers (where I drop gear and 1st notch of flaps).  In my case the top of the white arc and Vbg are about the same.  I can say from doing many power off approaches from downwind that flaps detract from glide distance more than most would think.

[T. Peterson]

1 hour ago, Shadrach said:

I can think of one scenario.  If I lost the engine after crossing abeam the numbers (where I drop gear and 1st notch of flaps).  In my case the top of the white arc and Vbg are about the same.  I can say from doing many power off approaches from downwind that flaps detract from glide distance more than most would think.

That’s good to know. I didn’t consider that scenario, but I will now. Thanks.

[Shadrach]

1 hour ago, T. Peterson said:

That’s good to know. I didn’t consider that scenario, but I will now. Thanks.

I’m sure you’d rise to the occasion. 
Whenever someone say “I would not do that”, the contrarian part of my brain starts running scenarios where what is typically a “no no” might be prudent.

[jlunseth]

On 7/21/2021 at 10:58 PM, KLudwick said:

I've given ~100 hours of Mooney dual this year and put another 50 on mine.  I have always used and taught the same technique: as soon as the gear is up in the wheels wells and you make a quick scan of the instruments, retract the flaps.  The quick scan of the instruments lets you ensure proper climb speed, directional control, etc, and prepare for the additional slight pitch change when you retract takeoff flaps.  For Johnson bar machines, in many cases the scan allows you to get back on proper speed and heading seeing as many owners let one or the other slip during gear retraction.  Cleaning the airplane up and capturing/maintaining your preferred climb speed sooner allows for better second and third segment climb rates as well.  

We all fly our machines a bit differently, which makes flying more fun (and creates good buzz and conversation on MooneySpace)!

This is what I do. Gear up when the VSI shows a positive rate of climb, flaps up when the gear is stowed. There was a really good article in AOPA’s magazine a few years ago about the impossible turn and engine failure on takeoff. The author went out and ran some actual tests. Neither Vx nor Vy worked very well for initial climb. Vx was too nose high, and with a slight delay to recognize the engine out condition (I think they used three seconds) the aircraft would stall before the pilot responded. Vy resulted in the aircraft reaching turn back altitude too far away from the airport to make it back. The best speed for initial climb was best glide. I use 85 kts which is in the best glide range but on the high side for my aircraft (the POH has a graph, best glide depends on gross weight on takeoff). It is roughly half way between Vx and Vy. So I want the aircraft accelerating to 85 kts as soon as possible. Therefore I raise the gear, and particularly the flaps the way I do, let the aircraft accelerate, and start my 85 kt climb as soon as I can. Fortunately I have never had to test this method in real life, i.e. with the engine having failed on takeoff, but I did some testing at altitude several years back when I did my commercial, and it proved out. If you have to do the turn back, it is a fairly aggressive turn, 45 degree bank as I recall, with the aircraft descending to keep 85 kt (for my aircraft). The turn back can be done in my aircraft from about 800 AGL if you are on your game, but I use 1000 ft all the same, because I don’t practice this maneuver and therefore am really not on my game.

[rbp]

In gliders we practice simulated toW rope  breaks at 200’.
 

There are a few additional points to add:

1.  Pitch for Vglide immediately 

2. Initiate the turn back aggressively 

3. Turn into the crosswind

 

[Hank]

2 hours ago, jlunseth said:

This is what I do. Gear up when the VSI shows a positive rate of climb, flaps up when the gear is stowed. There was a really good article in AOPA’s magazine a few years ago about the impossible turn and engine failure on takeoff. The author went out and ran some actual tests. Neither Vx nor Vy worked very well for initial climb. Vx was too nose high, and with a slight delay to recognize the engine out condition (I think they used three seconds) the aircraft would stall before the pilot responded. Vy resulted in the aircraft reaching turn back altitude too far away from the airport to make it back. The best speed for initial climb was best glide.

Hmmm . . . . 

For my C, Vx = 85 mph; Vy = 100 mph - altitude; Vbg = 105 mph. Thus, Vy < Vbg, so if Vy climbs too slowly, putting me too far from the runway, the faster Vbg would be worse!

What is the point in using Takeoff Flaps if they're only out for 3 seconds after liftoff? The times I use them, they stay out until I'm looking down at the obstacle I needed to clear, or when I'm happy with my heavyweight climb and have settled in and trimmed for initial climb.

[rbp]

45 minutes ago, Hank said:

For my C, Vx = 85 mph; Vy = 100 mph - altitude; Vbg = 105 mph

I am Very surprised to learn that Vy<Vglide. Usually it’s about 1/2 way between  Vx and Vy

 

I am also surprised to learn Vx and Vy are so high. In my M they are  85 and 105 kias 

 

[Hank]

Looks like I was wrong--Vx = 80mph!

[PT20J]

Recall that Vy is the speed where there is maximum excess power available over the power required for level unaccelerated flight. Increasing engine size will result in Vy occurring at a higher airspeed.

Vx is the speed where there is maximum excess thrust available over the thrust required for level unaccelerated flight. If the engine is large enough, Vx can theoretically be below stall speed. (If the thrust to weight ratio is greater than one, the airplane will climb vertically and Vx is indeterminant). Because the mathematical Vx may be too slow to be practical or safe, the manufacturer may just specify an operationally reasonable speed.

Skip

[DCarlton]

1 hour ago, PT20J said:

Recall that Vy is the speed where there is maximum excess power available over the power required for level unaccelerated flight. Increasing engine size will result in Vy occurring at a higher airspeed.

Vx is the speed where there is maximum excess thrust available over the thrust required for level unaccelerated flight. If the engine is large enough, Vx can theoretically be below stall speed. (If the thrust to weight ratio is greater than one, the airplane will climb vertically and Vx is indeterminant). Because the mathematical Vx may be too slow to be practical or safe, the manufacturer may just specify an operationally reasonable speed.

Skip

Having a surprisingly hard time processing these definitions …. Excess power vs thrust available.  Will have to chew on it.  

[jlunseth]

My book Vx is 71 and Vy is 96 KIAS. Both change with altitude of course. That can be an issue when flying the mountains out west. However, I don’t use Vx or Vy, they are pretty much useless. Vx is useful to me, only for true short field operations and general clearing of obstacles. Once or twice in 12 years I have used long Vx climbs to get out of a mountain valley and over the ridges. Normally I use my 85 kt speed for initial climb and then transition to an enroute climb speed. Vy is not useful at all, don’t think I have ever done a Vy climb in my Mooney. If going on a long trip I transition to a cruise climb that is full power, full rich, cowl flaps open, 500 fpm climb rate during the summer months. More interested in engine cooling and ears than theoretical climb over the ground.

Edited April 1, 2023 by jlunseth

[hubcap]

On 4/1/2023 at 8:35 AM, jlunseth said:

My book Vx is 71 and Vy is 96 KIAS. Both change with altitude of course. That can be an issue when flying the mountains out west. However, I don’t use Vx or Vy, they are pretty much useless. Vx is useful to me, only for true short field operations and general clearing of obstacles. Once or twice in 12 years I have used long Vx climbs to get out of a mountain valley and over the ridges. Normally I use my 85 kt speed for initial climb and then transition to an enroute climb speed. Vy is not useful at all, don’t think I have ever done a Vy climb in my Mooney. If going on a long trip I transition to a cruise climb that is full power, full rich, cowl flaps open, 500 fpm climb rate during the summer months. More interested in engine cooling and ears than theoretical climb over the ground.

I can’t fly at Vx for very long climbs in my M20K 231 without the CHT’s getting too high. After I get the gear up and flaps up and talking to ATC I usually cruise climb at 115-120kts up to altitude.