From: karl@ddsw1.mcs.com (Karl Denninger)
Subject: Re: Hinckley Crash
Summary: Gear and other stuff
Keywords: twin engine aircraft on tkof
Organization: Macro Computer Solutions, Inc., Chicago, IL
Date: Sun, 13 Sep 1992 18:40:05 GMT

In article <1992Sep11.143642.16020@bernina.ethz.ch> zari@bolzano.math.ethz.ch (Alain Zarinelli) writes:
>
>In article <BuE83F.K5q@ddsw1.mcs.com>, karl@ddsw1.mcs.com (Karl Denninger) writes:
>
>|> 1)	It appears they had an engine-out condition at or shortly after
>|> 	take-off.  I know this isn't a good time for such an event, but
>|> 	aren't most twins capable of climbing under these conditions even
>|> 	with a full gross payload?  
>|>                            [...stuff deleted...]
>
>     As I already tried to point out in a previous post to the net
>(cf article <1992Sep10.141119.16679@bernina.ethz.ch>. I can also e-mail
>you a copy of it...) this is NOT the case for _LIGHT_ twins (MTOW < 5.7
>tons, operating under FAR 23).

Yep, but I believe someone else posted the performance numbers for this
particular light twin.  Note that the Chicagoland area isn't far from sea 
level either.  It was a rather warm day (which doesn't help).  Does anyone 
know the density altitude that day (or the absolute altitude of Hinkley, 
which along with the temperature could make the calcuation trivial).

From the numbers given it would appear that the plane in question does have
a positive rate of climb with one engine at what I'd guess was the density 
altitude at the time of the incident.  This is >assuming< you have cleaned
up the airframe to reduce drag.

>|> 2)	The gear looked DOWN.  I distinctly saw TWO landing gear wheels in 
>|> 	the wreckage on local TV, and one was visible in the newspaper photos.
>|> 	Isn't it standard procedure, in the case of an engine out, to do
>|> 	>everything< possible to lessen drag?  I would think that one of the
>|> 	first orders of business is to hit the "gear up" switch -- [...]
>
>     Right, but it depends on the situation. If you still have enough RWY
>in front of you to land the aircraft you certainly wouldn't put your gear
>up, would you? 

At >three miles< from the runway you'd have enough left to land on? :-)

>|>                                                             [...] right
>|> 	after increasing power on the remaining (good) engine!
>              ~~~~~~~~~~~~~~~~                   ~~~~
>     NO WAY! You might even have to DECREASE power on the remaining engine
>in order to maintain control of the aircraft!

Perhaps.  I would suppose that would depend how far above Vmc you are at
that point, and whether you have sufficient airspeed (and therefore rudder
authority) to counter the torque moment of the remaining engine at a higher 
thrust setting.  In other words, the question of the moment is "can this
plane maintain a positive rate of climb, however small, and remain in
control."

If not, and you're too close to the ground to trade altitude for airspeed, 
then you're finished flying and ought to instead drop it on the best reachable
site (which the pilot in this case had >made< -- that soybean field).  

On the other hand, I can think of very little that would make this situation
(one engine out on a twin) worse than NO power available on a single in a
similar situation.  At least you have >some< power available.  The choice
here is whether it helps you to use it and whether the usable thrust is enough.

The point is that you have an energy management situation on your hands in 
any aircraft.  The first order of business is to keep the plane in the air 
and >flying<, which means below critical angle and above critical airspeed 
(i.e. stalls at 30' AGL can easily kill you).  Part of this is cleaning up 
the aircraft in order to increase the lift available in relation to drag 
(getting rid of drag is just as good as getting additional lift no?)

It seems insane that at some three miles from the field, which represents
a time greater than one minute from take-off, that the pilot would not have 
retracted the gear in the face of a known energy management problem (engine 
out condition).  He certainly wasn't going to need the gear to land in a 
soybean field!  

I'd love to know where the flaps were set at the time of the crash; the wing
wasn't visible in any of the press photos or TV coverage I saw.  Ditto as to
whether the dead engine's prop was feathered.  An unfeathered "dead" prop
would make the torque problem (rotational moment) even worse than usual due 
to its drag in the airstream.

I can well imagine that these three elements (prop feathered + flaps + gear)
could easily add up to more than enough to make the difference between "will
fly but clumsily" and "insufficient usable thrust to overcome drag" with an
engine out in a typical light twin.  Perhaps even >one< of these elements 
is enough to make the difference in this particular plane.

As to the person who posited a "CG shift"; the crash investigators reported
that the skydivers were all firmly braced for impact (presumably forward as
far as possible, being that there were no seats) when the plane hit the
ground.  That much they were able to determine.  It would, then, appear that
they had the "most favorable" CG in terms of position that was possible
under the circumstances.

As in all human endeavors which involve flight, mistakes tend to be rather
expensive in their life quotient.

--
Karl Denninger (karl@ddsw1.MCS.COM, <well-connected>!ddsw1!karl)
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