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Author Topic: Re: The Lae Takeoff - a closer look / consideration of take-off methods  (Read 6524 times)

Tim Gard

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I wonder if a 3 point takeoff (12.55) was ever considered appropriate?

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JNev

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Re: Re: The Lae Takeoff - a closer look / consideration of take-off methods
« Reply #1 on: September 28, 2014, 06:44:06 AM »

I wonder if a 3 point takeoff (12.55) was ever considered appropriate?

Great clip, Tim - I found the '3 point take-off' reference at around 6:40, and the take-off followed within a few seconds.

Don't know.  The B-17 had a big fin and rudder (and the instructor makes reference to rudder effectiveness at around "50"); it also had a comparatively flat angle of attack when sitting on 3 wheels.  But the big argument 'for' 3 point came at around the time frame you pointed to - the B-17's low angle of attack assured that its attitude was well below that of stall; the gradual build-up of lift would decrease wheel drag on a heavily laden airplane.  Nice arrangement, makes sense.

The L10 might benefit from the same, arguably.  It had had a nice pair of fins and rudders that looked generous enough, and a locking tailwheel I believe (like the 17), but it also appears to have significantly more angle of attack when sitting three point.  That suggests to me that the angle between 3 point and stalling angle left less margin and would create significantly more aerodynamic drag than would the 17.  That may answer why I've never seen footage of an L10 using the maneuver, as has been the case for types I've flown. 

I guess one would have to consider what advantage the 3 point take-off might have for the L10.  Take a look at it with the B-17 film (excellent explanation) as a guide: does the build up of lift develop fast enough to reduce wheel drag rapidly enough to produce a shorter ground roll?  At the L10's angle of attack in 3 point, I have some doubt - aero drag would be more significant in 3 point, and the wing does not appear to be in as sweet an attitude as the 17's (which now appears optimized for this maneuver by her designers, as I think about it); in fact the wing may be close to stall attitude in 3 point - very inefficient compared to the 17's 9 degree margin.  I doubt the L10 would gain the same advantages as the B-17 by using a 3 point take-off.

My reference to the rudder comparisons is a secondary thought: the twin Beech (model 18) had a reputation for being a bit wicked in transition from 3 point to mains only for take-off, and worse on landing, because the rudders suffered some blanking effect from the wing when in 3 point.  The technique, according to my uncle who instructed in the type for the navy and flew them a lot as transports, was to make a rapid transition from 3 to 2 on take-off once you had the speed for it, and the opposite on landing: 'wheel' it 'on' (land on mains only, fairly level attitude), then settle the tail deliberately as it slowed to a safe speed to do so and plant the tailwheel, which could help you control directionally at that point.  I don't know if the L10 was similar, but it does have a very similar lay-out - big wing and relatively modest twin rudders (combined they are 'big', individually they may have been subject to some loss of effectiveness in 3 point - not sure).

I've done 3 point take-offs in a number of taildraggers, but it was more for the sake of an exercise and to get a sense of where the bird would naturally unstick.  It was always a bit 'stilted' and somewhat close to stall attitude in all that I flew, except for the Maule. 

I had about 1000 hours in a Maule M4-220C (the M4 was the older, rounded fin model) - and it had a relatively high-sitting tail, i.e. low angle of attack.  It could be 3 pointed off very nicely and had a lot of power to weight, so would climb aggressively once off.  But it still did better by two-pointing 'off' - and in fact, some advantage could be had by locking the brakes, and powering up to raise the tail before the roll, then releasing the brakes gently at fully power (it is a bit delicate to coordinate).  The forward acceleration was fairly dramatic this way - aero drag very low; once into the roll and when ready to rotate (at around 50 knots), extend full flaps and rotate firmly.  The tailwheel often brushed the ground but the immediate climb angle was dramatic and the bird could sustain that with a moderate load until clear of 'obstacles' (50 feet assumed). 

I never did that in an actual critical field / obstacle situation, but for training and demonstration.  When that is done you fly like the engine wouldn't dare quit, obviously: the wing was flying, but close to the edge, and thrust vector had a lot to do with what was going on.  I guess I was young enough that I thought nothing bad could happen to me - would likely be more conservative today... 

I've forgotten the actual numbers, but it was remarkably simple, durable and able airplane and could do what I describe in a very few hundred feet of roll - like under 400 feet.  That technique arguably optimized the balance between wheel drag and aero-efficiency, but admittedly also had to do with demonstrating the airplane's extreme abilities.  A normal take-off was to simply start the ground roll with gradual power application, let the tail rise (good rudder at low speed in 3 point) more naturally, then off at around 60, and initial climb somewhere around 80, I think (been 25 years).

That was the preferred method in all the types I flew, which except for the Maule seemed to have had deck angles more approaching that of the L10 than the B-17.  The Maule was not as 'flat' as a B-17 on the ground, just seemed a bit less than the others I was familiar with (Luscombe, Cessna 140/170/180, Swift, etc.). 

Another comes to mind - I had the privilege of flying the rare Meyers 145, as a youngster: my dad owned one and made a point of drilling me in it for take-offs and landings - probably the most valuable tail-dragger experience I've had in life.  I was too young to solo that airplane, which was sold when I was 15, sadly, but did many take-offs and landings in it from the right seat, with no brakes.  It was docile - had a non-steerable but significantly raked tail-wheel - which sat at the end of an unusually long tailwheel strut.  As a result, it tended strongly to track straight with weight on all three wheels very nicely, even with crosswinds. 

That was a unique airplane - had a hand-pumped gear retraction system, and it taught me early on to handle 'complex' tasks while flying - fly 'first' - maintain heading and climb and stay heads-up and out while raising the selector handle between the seats, then pumping the long hydraulic pump handle - 21 strokes comes to mind, to get the gear up and locked.  Down was simpler - push the selector 'down' and the gear would gravity drop, and typically lock - but you would pump several strokes to pressurize it down (about four, I think).  Worked well, and there were emergency unlock releases at the inboard wheel well one could reach on either side of the cockpit, near floor.  I remember using the right one on one occasion for some reason, and then lubing the gear thoroughly after we were on the ground.

That long 'stalk' for the tailwheel gave the airplane better than average visibility forward, and looking back it sat with a fairly low angle of attack.  We did do some three point takeoffs in it - I recall them being docile with the airplane simply rising as it gained good flying speed.  One would then climb modestly as the airplane gained speed and left ground effect - a gentle exercise: it was not overpowered, having only a C-145 (Continental 145 HP) engine, but cruised nicely at around 130 knots.  It deserved 200 HP, IMO, and my dad always thought so.  The more typical take-off was two-point though, and seemed more effective - probably more aero-efficient.

Interesting perspective from the B-17, and very educational.  Don't know about the L10 - maybe we can find some commentary or footage.  Don't forget how Earhart lost control during take-off in Hawaii at Luke Field: I've wondered about what happened during the sequence - rudder vs. taking advantage of a locked tailwheel (I believe the L10 had that as standard, but may have been an option), her habit then of using differential power (admonished by Mantz to avoid that), etc.  Don't know - but these details make the thought interesting.
- Jeff Neville

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« Last Edit: September 28, 2014, 07:05:40 AM by Jeffrey Neville »
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Tim Gard

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Re: The Lae Takeoff - a closer look / consideration of take-off methods
« Reply #2 on: September 28, 2014, 03:25:43 PM »

Jeff,

Thanks for sharing your detailed account.
One thing about the war, its training and training films, is the great deal of effort that was put into simplification.
This video (06:05) shows Pan Am providing Air Force recruits with over water navigation training. 

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JNev

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Re: The Lae Takeoff - a closer look / consideration of take-off methods
« Reply #3 on: September 28, 2014, 04:19:53 PM »

Very cool stuff, Tim - thanks!

This is a history itself - how the dots got connected to train these guys for herculean efforts.  Amazing.

I'm hooked on watching every second of the B-17 thing for the moment - how often does one get 'dual' in one of those???  ;)
- Jeff Neville

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Tim Gard

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Re: The Lae Takeoff - a closer look / consideration of take-off methods
« Reply #4 on: September 28, 2014, 08:48:21 PM »


I'm hooked on watching every second of the B-17 thing for the moment - how often does one get 'dual' in one of those???  ;)

Jeff,

I share your enthusiasm.
So many training films for the warbirds are on the 'Tube.




 
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JNev

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Re: The Lae Takeoff - a closer look / consideration of take-off methods
« Reply #5 on: September 28, 2014, 09:19:45 PM »

Thanks for that, I'd not realized it before.  I'll enjoy that and sharing about it!
- Jeff Neville

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Tim Gard

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Re: The Lae Takeoff - a closer look / consideration of take-off methods
« Reply #6 on: September 30, 2014, 12:09:29 PM »

B17 3 point take offs are evident in 12 O'Clock High (37:40)

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JNev

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Re: The Lae Takeoff - a closer look / consideration of take-off methods
« Reply #7 on: September 30, 2014, 01:53:04 PM »

This reminds me that I learned soft field take-offs in the Cessna 140 -

Flaps (modest sized) were used; the tail wheel was allowed to rise, but a somewhat higher angle of attck was maintained than for the standard take-off. The B-17 take-off graphically illustrates why: aero forces begin to reduce wheel drag sooner (critical on soft turf) and the bird naturally rises from the ground as soon as lift is sufficient, shortening the labored ground contact time. Then one would hold the bird in ground effect long enough to gain a safe climb speed, and then be away.

The B-17 is an amazing airplane, and now realizing how she was optimized in gear stance to take advantage of this technique, she is all the more astonishing.  It worked well.
- Jeff Neville

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« Last Edit: September 30, 2014, 01:54:48 PM by Jeffrey Neville »
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