Flaps on take-off?

[Bob_Belville]

This would certinly qualify as a short field where I would use flaps......

 

This is kind of outside the scope of this discussion. We are talking about normal takeoffs, not edge of the envelope stuff.

Sure. But I have an uneasy feeling about not using flaps except for rare take offs, when I do have to execute a max performance scenario I am doing something I rarely do. Will I have the trim set ideally, will I hold Vx then Vy?

 

Perhaps the poor slob was just a careless pilot but perhaps some CFI taught him to never use flaps.  

[Shadrach]

At the risk of interrupting a pretty funny thread there at the end...

 

The "take off" marker on your flaps is the point at which the flaps start to add more drag than they do lift.  Up to and including that point, the flaps add more lift than drag.

 

Using "take off" flaps will result in a shorter takeoff roll and a steeper angle of climb, meaning your ratio of upward travel to forward travel will improve.  This is helpful for obstacle clearance.  It is also helpful for quickly putting distance between you and the ground and minimizing the amount of time you spend under 1000 AGL, which is the most dangerous time to have an engine failure.

 

That's the theory you can read on these forums.  I've verified it in both an M20C and an M20K.  I use takeoff flaps as a habit unless there's more than about 20 kts of wind.  I will then leave them up to minimize the gusting effect, and with those winds, takeoff roll and angle of climb are great anyways.

 

I spent quite a bit of time on the C model with inop flaps because of a pesky hydraulic leak.  It would take off just fine without them, but rolled longer and didn't climb as well.  It actually does have a nice feel to it that way.  The plane accelerates faster once you get in the air without the flaps.  But it doesn't perform as well.

 

You never know when your engine might quit shortly after takeoff, and I prefer to be as high as possible and as close to the airport as possible when it does.  No-flaps puts you lower and farther away.

Thank you Zane! I suspected the take-off flap position generated greater lift then drag but have not seen a reference and I didn't want to talk "out of school". Do you have a reference?

[Z W]

No official reference, I read it on the internet somewhere, probably on this site. However, you can confirm it with the plane's flight characteristics. Also, the performance charts for my C model specified that to reach Vy above about 10,000 ft, you must extend takeoff flaps. I did that and verified that is the case. If takeoff flaps increase climb rate, they must add more lift than they do drag. I also know that full flaps decrease climb, so I know they add more drag than lift.

I know, not exactly a scientific, peer-reviewed and published article by an aeronautical engineer, but those are hard to come by for our planes. This is easy enough to test yourself. Go compare your climb rates at a constant IAS and power setting both at no flaps, takeoff flaps, and full flaps. You should takeoff with whatever flap setting gives you the highest rate of climb at Vx, which is your target airspeed until obstacle clearance is achieved. Guess what? It's the setting labeled "takeoff."

Seems like a no-brainer to me. But if you just like taking off without flaps because of the rocket-like feeling in the seat of your pants as the plane accelerates to cruise speed, that actually makes plenty of sense to me too.

[Super Dave]

I would add 2 things.

 

1) I've read Kromer for years and just because he does it or did it at one time does not make it optimal. He also advocated leaning to 100 ROP immediately after take-off and flew many of his evaluation AC at sustained climb CHTs ranging from 420 - 450df for extended periods of time. http://mooneyspace.com/topic/10405-hes-moved-again-bob-kromer/#entry121890. I say no thanks to that advice, but to each their own.

 

2) Your analysis of no flap climbs ony takes parasitic drag into account. To be accurate, induced drag should also be accounted for, and the effective reduction in AOI will yield less induced drag at climb AOAs.  I've not seen the numbers, so I don't know what the net is. Probably not much...

1. I did not mean to suggest that we should all be doing no flap takeoffs because Bob Kromer says so. I was just making a counter point to all of the responses that stated with absolute certainty that configuring with takeoff flaps is the only proper way to fly a Mooney, and that anyone who suggests otherwise is clueless. Some were citing factory test pilots and POHs, and I thought using Kromer as an example of the no flap camp was ironic because he was a factory test pilot that had a hand in developing POHs.

2. Actually, my analysis takes total drag into account. You can try it out yourself by running a few climb tests. Establish a stabilized Vy climb at something like 500' AGL, give yourself another 500' to stabilize and start a timer passing through 1000', stop the timer passing through 3000'. Next, take another run from the same altitudes using takeoff flaps and compare the results. If CHTs are a concern, the test could be run at some arbitrary amount higher than Vy, but this will exaggerate the no flap advantage.

[jetdriven]

But you can agree that a flaps 15 takeoff results in a shorter ground run, a lower liftoff speed, and a shorter distance to clear obstacles, right?

 

Are there any benefits to a flaps up takeoff other than "it feels right" ?

[Immelman]

When I was new to Mooney ownership I did as you do. I did not see the point in using flaps if the runway was sufficiently long. I sucked the gear up and accelerated on up to Vy and went on my way.

 

Along the way several years back I got to thinking about engine failures after takeoff and what I would do should I be faced with that one day. I then started to do some experiments, looking at how high I was at the departure end of my home airport runway.

 

The difference between using takeoff flaps and no flaps astounded me. The initial climb gradient, pitching for about 90mph for that first 800-1000ft of climb is quite a bit steeper than taking off flaps up, and using up a whole lot more lateral distance to accelerate up to Vy (110mph +/-). After I saw this, and the safety it afforded with my own eyes I decided then and there to discontinue flaps up takeoffs on all but the longest of runways. Do as you please, but this is my practice.

[Hank]

If the obstacle is several thousand feet away, is there a benefit to taking off a few feet shorter and slower?

My home field is 3000' and I'm always at least 200 agl when I get there, and lower the nose from Vx to Vy.

Oh, I forgot, so many people here won't climb at Vy--better use flaps to make up for going Vy + 20 with gear down. Positive rate, gear up, hold Vx to clear the trees, complete climb at Vy; if heavy, positive rate, gear up, hold Vx to clear the trees, raise flaps while lowering nose to Vy.

For me, rotate at 70 mph; Vx = 80 mph; Vy = 100 - Alt. I climb at Vy as long as engine temperatures permit, and that is usually a concern only with summer weather. I climb the same way when departing with Takeoff flaps, except I'm heavy enough to need the extra lift (~800 lbs load or more, I use flaps, maybe 750, depending on weather and how I feel). This has worked well for over 450 tach hours, including instrument training. Come to think of it, my airline pilot CFII didn't say anything about no flap departures at home, either . . .

[jetdriven]

When I was new to Mooney ownership I did as you do. I did not see the point in using flaps if the runway was sufficiently long. I sucked the gear up and accelerated on up to Vy and went on my way.

 

Along the way several years back I got to thinking about engine failures after takeoff and what I would do should I be faced with that one day. I then started to do some experiments, looking at how high I was at the departure end of my home airport runway.

 

The difference between using takeoff flaps and no flaps astounded me. The initial climb gradient, pitching for about 90mph for that first 800-1000ft of climb is quite a bit steeper than taking off flaps up, and using up a whole lot more lateral distance to accelerate up to Vy (110mph +/-). After I saw this, and the safety it afforded with my own eyes I decided then and there to discontinue flaps up takeoffs on all but the longest of runways. Do as you please, but this is my practice.

 

500+ hrs M20E, CFI/II/MEI/ATP/fly for a living at an airline

A lot of these pilots reduce power to 25/25 which is bad in a lot of ways, but the reasoning for it is "for less noise".   If they were 500' higher they wouldnt need to reduce RPM for noise, as altitude is a pretty good noise barrier. And the Mooney is a rather quiet airplane, as some folks have demonstrated in 200 MPH low passes, it just doesnt make much noise to begin with. I'd argue no louder than a 172.

[jetdriven]

If the obstacle is several thousand feet away, is there a benefit to taking off a few feet shorter and slower?

My home field is 3000' and I'm always at least 200 agl when I get there, and lower the nose from Vx to Vy.

Oh, I forgot, so many people here won't climb at Vy--better use flaps to make up for going Vy + 20 with gear down. Positive rate, gear up, hold Vx to clear the trees, complete climb at Vy; if heavy, positive rate, gear up, hold Vx to clear the trees, raise flaps while lowering nose to Vy.

Yes, less wear on tires and wheel bearings, and less hopping around during the transition from light on the gear to solidly in the air.  Flaps at takeoff lower the speeds around ten knots.  Thats ten knots sooner you are flying and in control.  Is flaps up better than that?

[Super Dave]

But you can agree that a flaps 15 takeoff results in a shorter ground run, a lower liftoff speed, and a shorter distance to clear obstacles, right?

 

Are there any benefits to a flaps up takeoff other than "it feels right" ?

Shorter ground run-yes, lower liftoff speed-yes, shorter distance to clear obstacles-sometimes. If the obstacle is 50'-yes, if the obstacle is 1000'-no. Where is the break even point? I don't know, but I would guess that it is closer to 50' than 1000'.

Assuming that runway length or obstacle clearence is not a factor, I do count a few marginal advantages to no flap takeoffs. For example, I happily sacrifice some additional wear and tear on the tires/gear to realize better airspeed for engine cooling earlier in the climbout. I realize it's splitting hairs, but I'd rather split my hairs to favor CHTs over tires.

[BigTex]

When I was new to Mooney ownership I did as you do. I did not see the point in using flaps if the runway was sufficiently long. I sucked the gear up and accelerated on up to Vy and went on my way.

Along the way several years back I got to thinking about engine failures after takeoff and what I would do should I be faced with that one day. I then started to do some experiments, looking at how high I was at the departure end of my home airport runway.

The difference between using takeoff flaps and no flaps astounded me. The initial climb gradient, pitching for about 90mph for that first 800-1000ft of climb is quite a bit steeper than taking off flaps up, and using up a whole lot more lateral distance to accelerate up to Vy (110mph +/-). After I saw this, and the safety it afforded with my own eyes I decided then and there to discontinue flaps up takeoffs on all but the longest of runways. Do as you please, but this is my practice.

500+ hrs M20E, CFI/II/MEI/ATP/fly for a living at an airline

A lot of these pilots reduce power to 25/25 which is bad in a lot of ways, but the reasoning for it is "for less noise". If they were 500' higher they wouldnt need to reduce RPM for noise, as altitude is a pretty good noise barrier. And the Mooney is a rather quiet airplane, as some folks have demonstrated in 200 MPH low passes, it just doesnt make much noise to begin with. I'd argue no louder than a 172.

This is turning into one of those religious conversations where there's not a wrong answer. Next time you see Jerry Johnson ask him why he prefers no flap takeoffs and 25/25 climb outs. It's not because it feels right and less noise. His 5,000+ Mooney hours has a lot of Mooney cred in my book.

[fantom]

Next time you see Jerry Johnson ask him why he prefers no flap takeoffs and 25/25 climb outs.

 

Why don't you just tell us why you think Jerry, like you, doesn't use his flaps, Tex, and end our suspense.

[BigTex]

I never said he didn't use flaps Fantom.  He instructs to use flaps as the situation dictates.  But his preference is to not use them if he has runway length.  Also, what makes you think I don't use flaps?

[Super Dave]

When I was new to Mooney ownership I did as you do. I did not see the point in using flaps if the runway was sufficiently long. I sucked the gear up and accelerated on up to Vy and went on my way.

 

Along the way several years back I got to thinking about engine failures after takeoff and what I would do should I be faced with that one day. I then started to do some experiments, looking at how high I was at the departure end of my home airport runway.

 

The difference between using takeoff flaps and no flaps astounded me. The initial climb gradient, pitching for about 90mph for that first 800-1000ft of climb is quite a bit steeper than taking off flaps up, and using up a whole lot more lateral distance to accelerate up to Vy (110mph +/-). After I saw this, and the safety it afforded with my own eyes I decided then and there to discontinue flaps up takeoffs on all but the longest of runways. Do as you please, but this is my practice.

I respectfully disagree with your analysis. The engine does not care how far down the runway it is when it decides to fail, it is going to fail at a given point in TIME after power application. It may give you a sense of satisfaction to look at down at the departure end of the runway from 800-1000' after climbing out at 90mph with flaps, but in that instant, if you could look out your windscreen and see an identical airplane that had started its takeoff simultaneously with you, but had instead taken off with no flaps and climbed out at Vy, you would see an airplane that is farther down range, higher in altitude, and with more airspeed to play with in a glide. If both of your engines quit or blew a jug at this instant, which airplane would you rather be in? The kicker is that the imaginary airplanes CHTs are also cooler than yours as a result of the higher airspeed, so maybe his engine will last another minute and he'll be at 2000' when it develops a problem. Even better, if the imaginary airplane had been operated this way over the life of the engine, maybe it'll go another 100 hours before failure.

[Immelman]

I respectfully disagree with your analysis. The engine does not care how far down the runway it is when it decides to fail, it is going to fail at a given point in TIME after power application.

 

Agree completely. So how about a wager: Lets pick some time after power application where the engine quits (pull the throttle). Time begins at brake release. Try one takeoff flaps up, accelerate to best climb speed, then another with flaps 15 deg, pitch to about 90mph. The wager: tell me which one you like better with a failure at 30, 45, 60, and 90 seconds after brake release.

 

I dont advocate climbing all day like this .I dont want my cylinders cooking more than anyone else, and I cruise climb the heck out of my plane. Personally I find 600-800 agl sufficient to bring the flaps up and flatten out the climb, accelerating to cruise climb. But those first few moments of flight, starting when you dont have enough airfield left to land on straight ahead, and ending when you have multiple options for a safe forced landing - those are the most vulnerable moments of flight. That is the time I want to minimize. I am not an absolutist on this either... if its nothing but nice fields and long runways, I don't have a strong preference on the flap thing or whatever difference in ground roll it causes. Get up and go! But, there are plenty of airports in urban environments, or surrounded by trees or terrain, where a forced landing even with a nice roll-caged mooney will probably not have a good outcome. Those are the takeoffs I want to minimize my risk exposure on.

[Z W]

I respectfully disagree with your analysis. The engine does not care how far down the runway it is when it decides to fail, it is going to fail at a given point in TIME after power application. It may give you a sense of satisfaction to look at down at the departure end of the runway from 800-1000' after climbing out at 90mph with flaps, but in that instant, if you could look out your windscreen and see an identical airplane that had started its takeoff simultaneously with you, but had instead taken off with no flaps and climbed out at Vy, you would see an airplane that is farther down range, higher in altitude, and with more airspeed to play with in a glide. If both of your engines quit or blew a jug at this instant, which airplane would you rather be in? The kicker is that the imaginary airplanes CHTs are also cooler than yours as a result of the higher airspeed, so maybe his engine will last another minute and he'll be at 2000' when it develops a problem. Even better, if the imaginary airplane had been operated this way over the life of the engine, maybe it'll go another 100 hours before failure.

 

I think this is incorrect.  You assume the plane climbs faster without flaps, or to put it another way, that your rate of climb at Vy without flaps is greater than rate of climb at Vy with flaps.  Vy is actually achieved with 15 degrees of flaps, at least on some models.  I've attached the Vy charts from the POH of a 1968 C model, which specifies 15 degrees of flaps be used.

 

Interestingly, I just looked and the same chart in my current M20K model, also attached, which says "Flaps Up" for Vy.  So it's possible we have a difference between the short and mid bodies on this subject.  The same POH also specifies 10 degrees of flaps for best takeoff distance.

 

Also, it's not like using takeoff flaps results in standing the plane on its tail and roasting the engine at 450 dF.  We're talking about partial flaps until the plane is in the air and the gear is tucked up.  The quicker liftoff and higher initial climb rates very well might put your same theoretical plane well above its no-flap counterpart, at a higher airspeed, with cooler CHTs, at any given time during the first two minutes of flight.

68C Performance Charts.pdf

M20K 262 ROC Chart.pdf

[N201MKTurbo]

Would it be OK for a no flaps on takeoff pilot to dress up as a flaps on takeoff pilot for Halloween ? Or would that be politically incorrect?

[Super Dave]

Agree completely. So how about a wager: Lets pick some time after power application where the engine quits (pull the throttle). Time begins at brake release. Try one takeoff flaps up, accelerate to best climb speed, then another with flaps 15 deg, pitch to about 90mph. The wager: tell me which one you like better with a failure at 30, 45, 60, and 90 seconds after brake release.

 

I dont advocate climbing all day like this .I dont want my cylinders cooking more than anyone else, and I cruise climb the heck out of my plane. Personally I find 600-800 agl sufficient to bring the flaps up and flatten out the climb, accelerating to cruise climb. But those first few moments of flight, starting when you dont have enough airfield left to land on straight ahead, and ending when you have multiple options for a safe forced landing - those are the most vulnerable moments of flight. That is the time I want to minimize. I am not an absolutist on this either... if its nothing but nice fields and long runways, I don't have a strong preference on the flap thing or whatever difference in ground roll it causes. Get up and go! But, there are plenty of airports in urban environments, or surrounded by trees or terrain, where a forced landing even with a nice roll-caged mooney will probably not have a good outcome. Those are the takeoffs I want to minimize my risk exposure on.

Good idea, I'll try it next time I'm horsing around the pattern. I'm not an absolutist either; my goal in making these silly arguments is just to give the takeoff flap absolutists something to think about. I enjoy the debate, and maybe I'll learn something that will change my ways.

Just to be clear, I'll restate that I do not hesitate to use takeoff flaps when runway length or close in obstacles are a concern. I round the book numbers up and then double them. Even so, I find myself rarely using flaps.

[jnisley]

Am I still considered a Mooniac if I continue doing no-flap takeoffs on 5000'+ runways, as I've done for 500+ hours?

Why do I like no-flap takeoffs under (normal for me) conditions?

1. The plane is less squirrelly while on the runway (especially in windy conditions)

2. One less thing to forget during climb out.

3. ..............to be determined.

[PTK]

...He told me, that as a rule he never used flaps on take-off and recommended I do the same. I have now almost 50hours in the airplane and followed his advice. I never really felt, that I was missing out by doing no flaps take-off...Advice/recommendations?

"Never" to me means that he advocates you "always" take-off without T.O. flaps! Really?

Have you asked him if there is not one instance he can think of where you just might need flaps on take off?

What horrible advice! Talk about a CFI advocating and reinforcing very bad habits!

This is an absolute statement and by definition indefensible, and inexcusable coming from a CFI!

You never felt missing out because you've been following very faulty advice.

My humble recommendation would be to find a real CFI. Also sign up for a Mooney specific safety foundation seminar.

[jetdriven]

Am I still considered a Mooniac if I continue doing no-flap takeoffs on 5000'+ runways, as I've done for 500+ hours?

Why do I like no-flap takeoffs under (normal for me) conditions?

1. The plane is less squirrelly while on the runway (especially in windy conditions)

2. One less thing to forget during climb out.

3. ..............to be determined.

 

 

so, "it just feels right".  

[Super Dave]

so, "it just feels right".

It certainly does to the CHTs

[fantom]

The not so subtle distinction is that in a Mooney we should use TO flaps as SOP unless we have a well thought reason NOT to use them. Shorter TO roll and more immediate altitude is a good thing 'almost' always.

[fantom]

I never said he didn't use flaps Fantom. He instructs to use flaps as the situation dictates. But his preference is to not use them if he has runway length. Also, what makes you think I don't use flaps?

I just figured a guy who suggests spinning a Mooney is fun and safe wouldn't need flaps to TO Seriously though, I hope you misunderstood Jerry, and he more correctly said to NOT use flaps only if the situation dictated it. Maybe he was talking just for himself, and not for the myriad of less experienced pilots. Hopefully you can get him to visit MS and speak for himself.

[Mooneymite]

Do any of the Mooney models publish numbers for no-flap takeoffs on the POH?

 

My C model take-off numbers are for takeoff flaps.

 

Anyone ever seen any no-flap numbers from any source for takeoffs, OR landings?