Flaps on take-off?

[Shadrach]

You know guys, if you keep playing with your flaps like this you are going to go blind.

I was wondering why the knuckles on my right hand were growing hair.

[Super Dave]

I never mentioned L/Dmax. I was talking about L/D ratio at rotation.  If D is increased proprotionately more than L by adding take-off flaps at rotation, why does the airplane lift off sooner? It would seem that the additional drag would lengthen the amount of time and distance required to get to lift off speed even though that lift off speed is somewhat lower.

Sorry, I was sloppy with my notation, I should have written it as (L/D)max, or maximum lift to drag ratio. I was using (L/D)max to reflect the effect of flaps on the entire lift to drag curve.

Flaps will only add a very small amount of parasite drag on the takeoff roll. It's not until liftoff or near liftoff that the production of lift and induced drag have any significant impact on total drag. The small amount of additional drag up to that point is far outweighed by the lower speed required to liftoff.

[scottfromiowa]

At sea level on 100df day, mine says 1670ft to clear a 50ft obstacle (1070 to get airborne and 600 to climb 51 feet ). However those numbers are for MGTOW. I am usually much closer to or less than 2300lbs. At that weight, the numbers are 690ft ground roll + 505ft air distance = a total 1195 to clear the 50ft.  The margins are not as close as you think....but plenty close for me.

At sea level on 100df day, mine says 1670ft to clear a 50ft obstacle (1070 to get airborne and 600 to climb 51 feet ). However those numbers are for MGTOW. I am usually much closer to or less than 2300lbs. At that weight, the numbers are 690ft ground roll + 505ft air distance = a total 1195 to clear the 50ft.  The margins are not as close as you think....but plenty close for me.

Yes, 1550 for 1966 M20E (at gross on 100 degree day). One hot day with 30 gallons fuel, wife, daughter, dog & light luggage...and a really bad technique by me...the trees were cleared by what looked to be about 50 feet. I failed to rotate at 60-65 with T/O flaps and nose went high...stall horn, lower nose, trim, THEN gear and flaps....My lesson:

As others stated...technique and practice (by using T/O flap as POH states to do) makes for sound technique WHEN YOU NEED IT.

I wouldn't feel comfortable with those margins Ross, but I just don't have experience on sub-2000 feet strips in my plane.

I have enjoyed this debate and freely admit I have often NOT used T/O flaps at CID...I can use the practice and will start doing so...just like I converted to full flaps on landing due to MS. Thank you.

[DS1980]

Wow, this is still going? So when you beat a dead horse, is it easier to swing from above the head or use a side swing?

[N201MKTurbo]

Well after listening to all this very conclusive data, I'm still going to take off with the flaps up. I'm just a careless suicidal thrill seeker...

[Bob_Belville]

Well after listening to all this very conclusive data, I'm still going to take off with the flaps up. I'm just a careless suicidal thrill seeker...

Just so you know who to pray through in your hour of need, St. Jude is the Patron Saint of Fools.  .

[Super Dave]

ISTM that what Dave's physics application ignores is that drag is not constant but increases with speed and that drag from flaps is not as high at the lower speed required to lift off with the higher lift the flaps creates.

As I tried to explain somewhere back along this long and winding road - 'taint true. A wing with flaps extended (extended a little, or extended a lot) will always create a higher coefficient of total drag for a given coefficient of lift when compared to a flaps up wing.

[Super Dave]

Wow, this is still going? So when you beat a dead horse, is it easier to swing from above the head or use a side swing?

After page 4 I decided to rent a power dead horse beater; at this point, it would've been cheaper to just buy.

[gregwatts]

Well after listening to all this very conclusive data, I'm still going to take off with the flaps up. I'm just a careless suicidal thrill seeker...

 

But you gotta wear the flip flops..........!

[DS1980]

After page 4 I decided to rent a power dead horse beater; at this point, it would've been cheaper to just buy.

From Harbor Freight or Aircraft Spruce? I think the one from Harbor Freight is a little cheaper but doesn't have the automatic "Flaps or no flaps for TO" mode like the one from Spruce. But I think it is programmable. Oh and it can be used with the Switchbox. Bam!

[Hank]

But you gotta wear the flip flops..........!

How about a cool hat instead?

[Super Dave]

From Harbor Freight or Aircraft Spruce?

I have a guy

[Bob_Belville]

Want to try it w/o flaps?

[DS1980]

Please....everyone...the humanity.....just stop.

[201er]

I know. Using flaps on takeoff makes as much sense as flying LOP, using camguard, and owning a Mooney!

[DS1980]

Good grief. Page 8!!!

[Bob_Belville]

Good grief. Page 8!!!

Quit clicking on our thread. 

[DS1980]

It's like a car wreck...gotta watch!

[N201MKTurbo]

So who here has opened their storm window above 150 MPH?

[Bob_Belville]

Not that 

 

So who here has opened their storm window above 150 MPH?

Not that I recall... but I have flown with cowl flaps open above their placard ias limit. (Welding a cracked cflap this month!) 

[DS1980]

So who here has opened their storm window above 150 MPH?

The storm window is only for use for pilots who take off with flaps. It should be placarded as such.

[Hank]

So who here has opened their storm window above 150 MPH?

 

I don't believe I have ever opened mine above taxi speed. After runup and taxi are done, windows closed, door locked, seat belts checked, throttle forward. Oh, yes, I do open the storm window on rollout when it's warm, but not until I am comfortable letting go of the yoke. Since I don't move my toes to the brake until 50 mph, I won't be reaching for the window until after that.

[Bob_Belville]

I don't believe I have ever opened mine above taxi speed. After runup and taxi are done, windows closed, door locked, seat belts checked, throttle forward. Oh, yes, I do open the storm window on rollout when it's warm, but not until I am comfortable letting go of the yoke. Since I don't move my toes to the brake until 50 mph, I won't be reaching for the window until after that.

I opened the window on 9249M on long final into KTOL so that I could reach out and scrap ice off the windshield after a descent through a 1000' ceiling. I was standing on the right rudder to see the runway through the side window.  

 

What's the windchill factor @ 33F & 120 MPH?

[Hank]

 

What's the windchill factor @ 33F & 120 MPH?

Too cold for me, Bob!!

[tomn]

I opened the window on 9249M on long final into KTOL so that I could reach out and scrap ice off the windshield after a descent through a 1000' ceiling. I was standing on the right rudder to see the runway through the side window.  

 

What's the windchill factor @ 33F & 120 MPH?

Wow Bob, we need to get together one of these days. I need to hear more about these sort of things you did in my (your) plane!

Tom