Warbird Information Exchange

Found this statement in a post on another website.

The discussion surrounds Vmc and how aircraft configuration affects it.



So, they seem to be saying that raising the gear during a single engine failure with the other three at max takeoff power would produce a rolling moment that would cause the airplane to "roll right over".

That just doesn't seem right to me, but I have zero time in command of a B-17.

Can anyone with some B-17 experience comment on this?

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That's interesting. I'm not a pilot, but slept at Holiday Inn last night and have worked on a -17. The gear is electric, so I don't think you should have any asymmetrical issues as with a hydraulic system. I don't recall ever seeing anything in a manual where the gear is sequenced one before the other. We'll see shortly I'm sure.

Every time we've run the gear on Liberty Belle, both mains have hit the upstops at nearly the same moment. I can't imagine how that would cause a rolling moment on the airplane.......

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Rod Schneider
Ball Ground, Ga

Randy,

I have some training documents from one of the B-17 Transition Schools that might have information on such a situation. It'll take some time to even find the paperwork....... As Rob said, the two mains usually retract at very nearly the same rate even though they have individual motors and retract jackscrews.

Scott

Hi guys,

At the risk of making myself look stupid I am going to suggest it is to do with stability. From what I recall from my commercial flight training (embarrassing as I should be able to say this with certainty for that reason!) I remember a quote from my ex RAF instructor saying stability is akin to how you prefer your women - light and dirty or heavy and clean!! Light and dirty referring to gear obviously and that being the better scenario (I hope I am not offending anyone!).

Maybe someone could shed more light on this and/or confirm...

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"A B-24 was the box a B-17 came in!" - One crew teasing another circa 1944!

Well, the idea would theoretically be that Vmc with one engine failed and the gear hanging would be lower than Vmc with the gear up. This would mean that by raising the gear, the airplane would be below Vmc and cause the airplane to be unable to control.

So, I guess really there are two questions to be answered here:

(1) Does Vmc in the B-17 change when the gear is retracted, and
(2) is the power asymmetry in a single engine out takeoff situation such that below Vmc (or close to it) that the airplane would "roll over"?

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From the 1943 B-17F Pilot's Manual:



All the best,
PB

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Paul Bellamy

401BG Association Historian & Honorary Life Member
401BG Historical Society (UK) Member
1st Air Division HQ Historical Society (UK) Founder Member
Director of Archives & Collections, Airfield Research Group Archive, Alconbury
RAF Alconbury Base Historian

Hey Randy-

I don't have my training materials to hand, so I'm talking off the top of my cranium but I've never heard of any effect raising the gear has on Vmc or stability. The AZ Wing uses 92kts for Vmc on Sentimental Journey. Our listed Vs1 is 87 and Vso is 77. Our gear retracts simultaneously or nearly so, and frankly there is not a lot of drag penalty with the gear extended so we usually leave them out on crew training patterns to save cycles on the gear motors. There doesn't seem to be any difference between doing a normal pattern and an engine-out pattern with gear up or down, at least in my experience, and I've never heard any of our experienced PIC's or instructors talk about not raising gear with an engine failure. Then again, we're never operating near or over max gross weight, either.

Engine problem/failure of the No.3 engine on take-off with resultant swing to the right was what caused the B-17G, F-BEEA to crash and burn at RAF Binbrook during the filming of 'Memphis Belle' back in 1989. I wonder if the gear was down or up at the time in that incident.....??

I asked my Dad, who was a 15th AF B-17 pilot, and he said he never heard of any kind of roll induced by low speed,
gear in transit, engine out problems. If such an incident did occur, I would guess that the airplane simply stalled, and with the corrective rudder for the engine out, rolled in that direction.

Steve G

My two cents...I never flew B-17s but flew four engine aircraft (C-130s) in the USAF Reserve. The only thing I could see the gear retraction affecting is control authority from using up most of the available hydraulic pressure but B-17 flight controls are all manual/cables. I suppose if the gear retracted unevenly it could have some effect on directional control but not much. Even losing an inboard engine only modestly affects directional control. Upon losing an outboard engine the pilot would ensure max power on the three good ones (directional control allowing), feather the dead one, a little wing bank (5 degrees) into the two good engines and keep speed at or above three engine Vmc. Then again, maybe I'm missing something...

One additional thought--the gear on a Fortress retracts and extends rather slowly regardless of the situation. Any adverse effects should have been slow in developing if one side didn't retract and the other was in transit. The electric retract/extend system is simple but it takes that jackscrew a lot of revolutions to get the wheel in the nacelle.

S

By having the landing gear extended it has a keel effect much like a sailboat that although increases drag reduces the roll and yaw tendency.

Randy,

Somehow,I think that the person posting on the other website had an imperfect understanding of the situation.Retracting the gear won't cause the B-17 to roll even if only one main gear retracted.The only concievable theory that I can think of might be that the lowered gear could function as an additional vertical surface.

I looked in the B-17 Pilot Training Manual and have posted below what it has to say about the proper technique for single or two engine failure on take-off.It does mention that the airplane probably won't maintain altitude on two engines at weights over 58,000 lbs.Most B-17's at full combat take-off weights were probably at least 60,000 lbs.The published max gross weight for the B-17,at least according to the FAA for a type-rating was 59,000 lbs.

The instructions below also mention that you might be better off keeping an sick engine running as long as it's developing useful power and that it will be difficult mentally to hold the nose down when you're just barely flying and close to the ground.How true.By the way,I can confirm the last statement in red concerning the airplane floating more than expected on a single engine landing.

If you were near a stall and retracted the gear, would the CG move aft enough to reduce stability? I wouldn't think the CG would move much, but sometimes these effects can be magnified at high gross weights/high wing loadings.