Flap Retract on Takeoff

[carusoam]

There is a time frame stated in the MM for on the ground retraction... (Ross @Shadrach is the go to guy for the flap system details...)

In the air, it might be half that...

Vx is about clearing obstacles...

And procedures are clear about not changing configuration until clear of obstacles....

And flaps get you off the ground faster than no flaps...

And Because keeping an eye on everything out the window, and the airspeed and attitude required....

Those would be the reasons I use flaps for T/O...

 

Now... to find the time sequence for flap retraction in the MM... got one?
 

There may be one around here somewhere....

Best regards,

-a-

[RLCarter]

1 minute ago, moontownMooney said:

What should it be?

There is a “Time” specified in the manual while on the ground, it takes very little movement on the adjuster and the jam nut will also change the amount of time it takes

[vorlon1]

I read somewhere (the maintenance manual?) they should be adjusted so it takes approximately 10 seconds to retract from full down. 

Check your manual. 

[Hank]

When I use flaps for takeoff (leavng my old 3000' base on vacation, or with 4 people, or leaving the nearby 2000' grass strip), the flaps are for obstacle clearance. Once I'm looking down at the obstacle, flaps come up. But they're electric, so I don't get to do anything about the speed except maybe pause during retraction. Initial climb is always at Vx for obstacle clearance if needed, then nose down for Vy to altitude.

[steingar]

I use a couple pumps of flaps for takeoff.  Book says to, and it does save some wear and tare on the gear.  I suck up the gear fast on takeoff, soon as I see climb.  I wait too long and the forces on the bar are too much.  Flaps go up quick too because my flap speed is really low and easy to blow through.  So flaps come up just as soon as the gear is stowed.  I haven't noticed any loss of lift at all.  I can't claim that this will get me out of everything, though so far I've blasted out of a 2500 foot heavily occluded grass strip and a 2200 foot strip on an island.

[MooneyMitch]

3 hours ago, steingar said:

I suck up the gear fast on takeoff, soon as I see climb.  I wait too long and the forces on the bar are too much

Thats the same reason I gave my flight instructor regarding my decision to retract gear just after liftoff.

Instructor’s reply....... if you maintain your 80-90 mph speed ( isn’t that kinda close to our Vy?) till runway disappears and then retract, the forces on gear and bar are much the same as those lower forces when you retract just after liftoff.

I have applied this method and the instructor is correct....... it is true.

As I said, I only do this if she’s not peeking out her hangar door when I take off..... LOL ! 

Just a thought.

[Hank]

Just now, MooneyMitch said:

Thats the same reason I gave my flight instructor regarding my decision to retract gear just after liftoff.

Instructor’s reply....... if you maintain your 80-90 mph speed ( isn’t that kinda close to our Vy?) till runway disappears and then retract, the forces on gear and bar are much the same as those lower forces when you retract just after liftoff.

I have applied this method and the instructor is correct....... it is true.

As I said, I only do this if she’s not peeking out her hangar door when I take off..... LOL ! 

Just a thought.

But doing it that way keeps you much closer to the ground for more time--ask her the benefit.

Why keep gear down for more drag until you can't see the runway? At what point in your gear down climb can you no longer descend and land on the runway you can still see?

[MooneyMitch]

18 minutes ago, Hank said:

But doing it that way keeps you much closer to the ground for more time--ask her the benefit.

Why keep gear down for more drag until you can't see the runway? At what point in your gear down climb can you no longer descend and land on the runway you can still see?

Maybe I’ve confused the issue...... Vy best rate of climb.......doesn’t that get you most efficient altitude and distance above ground, and not keeping you close to the ground?

Her belief is should the engine fail, having the gear down till past runway will offer one less thing to deal with returning to the runway for landing.

What ‘cha think? 

[ShuRugal]

Maybe I’ve confused the issue...... Vy best rate of climb.......doesn’t that get you most efficient altitude and distance above ground, and not keeping you close to the ground?
Her belief is should the engine fail, having the gear down till past runway will offer one less thing to deal with returning to the runway for landing.
What ‘cha think? 

You will climb faster with the retracted than extended. The gear adds a lot of drag when extended. Drag means more power required for the same speed. Power is required to climb. If you are using power to shove the wheels through the air, that power isn't being used to climb.

I typically notice an increase of ~200 fpm at Vx when I suck up the gear. In the event of an engine failure 1 minute into climb out, that 200 feet could be the difference between life and death.

If you are operating from short field with obstacles, Vx retracted will get you a steeper climb than Vx extended.

Even if you have an engine failure at the exact moment you retract the gear on takeoff... So what? It takes two seconds to extend them again. If you don't have that two seconds, the plane became property of your insurance underwriter the moment the prop stopped. A belly landing is perfectly survivable. Landing on the departure threshold with your gear out might not be, if there's less than 500' between the threshold and the trees.

[steingar]

1 hour ago, MooneyMitch said:

Thats the same reason I gave my flight instructor regarding my decision to retract gear just after liftoff.

Instructor’s reply....... if you maintain your 80-90 mph speed ( isn’t that kinda close to our Vy?) till runway disappears and then retract, the forces on gear and bar are much the same as those lower forces when you retract just after liftoff.

I have applied this method and the instructor is correct....... it is true.

As I said, I only do this if she’s not peeking out her hangar door when I take off..... LOL ! 

Just a thought.

I might mention to the know-it-all CFI that vintage Mooneys are notorious for inefficient engine cooling.  A really good way to heat up your engine is to maintain a slow airspeed at high power.  I suck up the gear and flaps fast, and lower the nose for a cruise climb.  I expect my engine likes that better.  If the know-it-all CFI continued with his BS he'd be invited to exit the aircraft as soon as I turned around and landed provided he could keep his big know-it-all gob shut.  Barring that I might invite him to depart the airplane immediately.

I might also point out to the empty-headed bed-wetting food-trough-wiper who has the brains of a hamster and smells of elderberries CFI that the gear is very very draggy, and leaving it out robs you of energy that you could otherwise use to get that much more altitude, which is safety.

[Hank]

1 hour ago, MooneyMitch said:

Maybe I’ve confused the issue...... Vy best rate of climb.......doesn’t that get you most efficient altitude and distance above ground, and not keeping you close to the ground?

Her belief is should the engine fail, having the gear down till past runway will offer one less thing to deal with returning to the runway for landing.

What ‘cha think? 

Vy is the best rate of climb over time; Vx is the best rate of climb over distance. To get over an obstacle that's two miles away, I'd climb at Vx.

On the "visible runway" thing:  what distance does it take you to descend power off from 400agl? Once the end of the runway is less than twice that distance in front of you, you can't land on it and stop; once the end of the runway is that distance in front of you, you can't land on it at all. On a 4000' runway, I can easily be 400-500 agl by the time it passes under my wing. I probably couldn't land on the remaining runway much past the midpoint of those 4000', so keeping the wheels down beyond that point is both useless [you can't land] and counterproductive [the drag reduces climb rate and keeps you in the danger zone (too low to turn back) longer].

So just like on a touch and go or missed approach, on takeoff I verify positive rate then Gear Up!

Have we beaten this horse dead enough yet? 

[Ragsf15e]

59 minutes ago, ShuRugal said:

You will climb faster with the retracted than extended. The gear adds a lot of drag when extended. Drag means more power required for the same speed. Power is required to climb. If you are using power to shove the wheels through the air, that power isn't being used to climb.

I typically notice an increase of ~200 fpm at Vx when I suck up the gear. In the event of an engine failure 1 minute into climb out, that 200 feet could be the difference between life and death.

If you are operating from short field with obstacles, Vx retracted will get you a steeper climb than Vx extended.

Even if you have an engine failure at the exact moment you retract the gear on takeoff... So what? It takes two seconds to extend them again. If you don't have that two seconds, the plane became property of your insurance underwriter the moment the prop stopped. A belly landing is perfectly survivable. Landing on the departure threshold with your gear out might not be, if there's less than 500' between the threshold and the trees.

To be fair to the CFI, most are taught this way.  Whether it’s right or wrong may depend on the situation.  That’s why we all need to use our brains and community experience to develop safe techniques and  then think through situations that require different techniques.  Sticking to a technique that is good in a particular situation just because that’s what we were taught is a bit too rigid thinking.

Maybe the Cfi trained at “All Atp” on a 12,000’ runway with flat terrain and no obstacles in a Piper Arrow.  Leaving the gear down while a landing on the runway is possible might be a reasonable technique.  It’s also possible that’s exactly what the faa examiner wanted to hear.  The best instructors know the difference between technique and procedures and can listen to reasonable arguments to come up with new techniques that apply to different situations.

[MooneyMitch]

"Have we beaten this horse dead enough yet?"...................Not really, well maybe............ we can continue to discuss, but............we can change over to beating horses with  LOP vs. ROP, or wet tanks vs. bladders.............or? Just kidding of course.

Hey, what about the side step departure theory which would offer you only a 180" turn back to the field as opposed to a straight out departure engine failure resulting in the dreaded 220 degree or so turn back the runway?  What do you think about that?

[MooneyMitch]

1 hour ago, steingar said:

I might mention to the know-it-all CFI that vintage Mooneys are notorious for inefficient engine cooling.  A really good way to heat up your engine is to maintain a slow airspeed at high power.  I suck up the gear and flaps fast, and lower the nose for a cruise climb.  I expect my engine likes that better.  If the know-it-all CFI continued with his BS he'd be invited to exit the aircraft as soon as I turned around and landed provided he could keep his big know-it-all gob shut.  Barring that I might invite him to depart the airplane immediately.

I might also point out to the empty-headed bed-wetting food-trough-wiper who has the brains of a hamster and smells of elderberries CFI that the gear is very very draggy, and leaving it out robs you of energy that you could otherwise use to get that much more altitude, which is safety.

I love Monty Python too!! 

[Ragsf15e]

47 minutes ago, MooneyMitch said:

"Have we beaten this horse dead enough yet?"...................Not really, well maybe............ we can continue to discuss, but............we can change over to beating horses with  LOP vs. ROP, or wet tanks vs. bladders.............or? Just kidding of course.

Hey, what about the side step departure theory which would offer you only a 180" turn back to the field as opposed to a straight out departure engine failure resulting in the dreaded 220 degree or so turn back the runway?  What do you think about that?

Personally I don’t use that but I would if i was departing close to straight out.  I normally fly off a busy, tower controlled airport with shortish parallel runways and terrain on one side, urban area all around (ksff).  There’s no way to offset and nowhere to land.  It’s uncomfortable.  I don’t practice patterns here but my hangar is here.  Instead, I turn crosswind as early as possible within reason. That gives me a few more options.

At non towered fields I suppose you could but be careful you don’t end up a conflict with someone else who’s expecting you to be in a normal part of the pattern.  Also the AIM says we should turn crosswind within 300’ of pattern altitude, so I usually turn there to remain predictable and seen. Always think there could be an airplane without a radio or adsb or transponder operating legally in the pattern with us.

 If there’s good fields for landing around, I’d fly a normal departure and pattern as much as possible and keep the fields in mind, turn around is pretty dangerous at low altitude without power even if some of the turn is out of the way.

[Hank]

Offset takeoffs? Hmmm . . . .

At my first base [KHTW], departing 26 with a sidestep away from downwind would put you into the parallel ridge, a poor safety result.

At any airport with parallel runways, direction of sidestep would vary with which runway you are on and which way you are going. At KBNA, you can't sidestep at all on 2 / 20 C, better not sidestep either way! Moving the wrong direction because it's what you're used to doing can end badly . . . .

So this habit can get you into trouble away from your frequently-visited fields. I think I'll not teach myself this bad habit.

[MBDiagMan]

Off the runway, positive rate of climb, gear up, flaps up.  Super simple.  A short runway with obstacle I would leave flaps in until obstacle was cleared.

[MooneyMitch]

Additional information to my “what if” delaying gear retraction posts, our main runway is 8K and our intersecting runway (about 2/3rds of the way down the main runway) is just over 5K feetsies.

If I did leave gear out for longer and with an engine out, I could maybe land on long runway or maybe land on intersecting runway, with gear still extended, depending on my location at time of the malfunction.

And because our field is so large (relatively speaking) and unpopulated, I could conceivably side step a bit on departure without causing a frakus with downwind traffic, buildings, etc.

Also, we’re 290 ft. above sea level and our ocean influences keep our temperatures pretty cool on an average basis ( maybe 70 or so).  Little if any density altitude to consider.

Our terrain is flat as a pancake till several miles away from our field.  No obstacles.  

Just thoughts here.

[Hank]

18 minutes ago, MooneyMitch said:

And because our field is so large (relatively speaking) and unpopulated, I could conceivably side step a bit on departure without causing a frakus with downwind traffic, buildings, etc.

Just be vigilant when away from home, where your new habit may cause problems. At KHTW, the ridge to worry about is between the runway (preferree is 26) and downwind for 8 . . . . Don't sidestep too much . . . .

[MooneyMitch]

44 minutes ago, Hank said:

Just be vigilant when away from home, where your new habit may cause problems. At KHTW, the ridge to worry about is between the runway (preferree is 26) and downwind for 8 . . . . Don't sidestep too much . . . .

Thanks for that.  Yes, definitely keep in mind applicability for sure.

As I’d said, I’m mostly not doing these methods, just throwing out for discussion and opinions..... the beauty of our MS!!!

[steingar]

Never side stepped a takeoff in my life.  Runway heading until I hit 500 feet and then on my merry.

[Shadrach]

On 7/15/2020 at 11:24 PM, moontownMooney said:

Thanks for all the good thoughts. I hadnt considered that perhaps our flaps are retracting too quickly and need adjusted. It is slower on the ground, but in the air they seem to substantially retract in a second or less and completely retract in under two seconds. What should it be? Our Vfe is 125 mph so that isn't a concern. For the folks talking about keeping flaps until 1000' and not changing configuration low... Vx and By are specifically with no flaps and I need that performance. Our home base (at least until a hangar opens up at a nearby field) is 2600' grass surrounded by 500-700' hills. This is why I care about being able to accelerate to Vx as quickly as possible. We currently derate our max gross by 200 or 300 lbs in the dead of summer to maintain reasonable safety margins.

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I shoot for about 10secs on the ground. A little over is just fine, much less is sub-optimal.

 

[Ibra]

Gear UP as I lift off and I get positive rate of climb, it deoes makes a huge difference on "acceleration" between VS and VX but has less effect on "climb angle" (it reduces both climb rate and climb speed), this matters in high density altitude takeoffs and I really don't care about landing gear up or dn with a dead engine after an EFATO as much as nailing my speed and reaching nearby field if Gear helps with that I will pull it, if not leave it where it is...

Flaps UP, in ground effect the impact is not clear: retracting takeoff flaps between VS1 and VS kills your liftoff while between VS and VX helps your acceleration to VX, in the climb the impact is not clear neither: flaps up slides your polar curve near VX so you have new VX1 which is roughly VX+(VS-VS1) but kills your ROC and you have a new ROC1

So it really depends on spreads between the various stall speeds VS1, VS, VX as well the rate of climb ROC(VS1, VS, VX) you see on these speeds with/without flaps 

To avoid complicating the story, I suggest you find the ROC at VS with takeoff flaps and compare it to the loss of ROC at VX with/without flaps and make your mind if retracting them while you accelerate between VS and VX make sense, retracting them bellow VS simply does not make sense 

I personally don't like to dynamically fiddle with M20J flaps on takeoff, I set them before full power and take them out away above obstacles, but I do play with them in Cub takeoff as follow: clean, landing, takeoff, clean, it seems to add few extra feets on top of the runway end but not something that saves a tight day as some claim (or maybe I am not that good with flaps, speed, yoke coordination )

Edited July 17, 2020 by Ibra

[M20F-1968]

 

On 7/15/2020 at 11:24 PM, moontownMooney said:

Thanks for all the good thoughts. I hadnt considered that perhaps our flaps are retracting too quickly and need adjusted. It is slower on the ground, but in the air they seem to substantially retract in a second or less and completely retract in under two seconds. What should it be? Our Vfe is 125 mph so that isn't a concern. For the folks talking about keeping flaps until 1000' and not changing configuration low... Vx and By are specifically with no flaps and I need that performance. Our home base (at least until a hangar opens up at a nearby field) is 2600' grass surrounded by 500-700' hills. This is why I care about being able to accelerate to Vx as quickly as possible. We currently derate our max gross by 200 or 300 lbs in the dead of summer to maintain reasonable safety margins.

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The hydraulic flaps should retract on the ground in about 9 seconds with aircraft stopped.  The time for retraction will be less in the air.

John Breda

[moontownMooney]

Thanks all. To follow up, we confirmed that our flaps are retracting too quickly (5.5 s on the ground) which is causing the uncomfortable rapid pitching/climb-pause when flaps are raised at appropriate speed (80-90 mph). We have tested being prepared to rapidly counter the pitch (until we can get our flaps adjusted) and our experience seems to confirm that raising them sooner (80-90mph) allows you to accelerate to Vx and/or Vy quicker.

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