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Subject: Re: emergency decents
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Hilton Goldstein wrote:

> >I can get about the same descent rate
> >either way, but there's no surprise at the ground level; it's
> >going to take a heck of a lot longer to land from Vno than from
> >Vfe.
 
> It appears that you are basing your entire emergency descent procedure 
> on what happens in the last few seconds. 

No,I'm not.  Why would you form that opinion?

It appears you are misunderstanding what I am writing.

I am saying:
	*one method will give descent rate X, but will result
         in problems in rough air, possible flirting with Vne
         in a slick plane, and lots of excess speed IF one wishes
         to land at the bottom of the descent.

	*another method will give descent rate ~x in the planes
         in which I've tried it, will handle rough air just fine
         and stay away from Vne, and will allow a rapid and easy
         transition to a landing.

Now, which descent is appropriate depends upon the reason for the
descent, the type of plane, and what's necessary to do at the
end of the descent.  If the goal is to lose altitude in smooth air
because of loss of pressurization, or the plane is a jet or turboprop
where a severe slip may be dicy, obviously the former is a better
choice.  The former may be a better choice IMC.

If the goal is to put the plane on the ground absolutely as soon
as possible, the latter may be a better choice.

If the plane has been structurally damaged, neither is probably
advisable.

Hope this clarifies what I've been trying to say.

> My procedure (from flight testing): power idle, nose down at Vne or 
> Vno, with a slip and/or turn.  As I near the runway, the airspeed goes 
> away very quickly as I'll hold an aggressive slip and I land.

This is where I believe your premise to be faulty.  How often have
you tried this portion of the procedure (transitioning from Vno or
worse Vne to a full stop landing)?

It just isn't generally true ("the airspeed goes away quickly" part).
Don't base a general procedure upon what's true for a C172 or a
Piper (and even taper wing vs Hershy bar wing Pipers are different)
but even in those I think it may take longer to bleed off the extra
speed of Vne than you think.  

In general, it's physics.  If you start out by *gaining* airspeed, 
you will initially descend faster.  But the energy gained by that 
extra airspeed has to be lost somehow.  There's not a free lunch.

Slicker planes like 4 place Grummans, Mooneys, Bonanzas, maybe
even Katanas, just don't give up airspeed quickly or willingly,
even with full flaps and a slip. And many of these planes have
very low Vles and Vfes (Mooneys come to mind) and not particularly
effective flaps (Mooneys, Grummans), so you can't change the energy
equation by adding extra drag until you've already lost that extra
speed.  Even a C182rg takes a while to slow down to the point where
the gear can be lowered.

As for descending at, or even near, Vne, I think it is very dangerous
advice *particularly* if you put a turn or a slip into the mix, if
there's an emergency to handle, and particularly with a slick plane.
Vne means never.

I note that the procedure John's POHs and instructors recommend does
NOT suggest Vne.

> Who's going to get down sooner?  I know I'll start descending 
> immediately, you won't.  I know my descent rate will be a *lot* 
> greater than yours

This is incorrect (based on flight tests).  The descent rate at the
top of the white arc, dirty plane, full slip, is approximately the same
as that achieved by clean plane, Vno, moderate bank (say 30 degrees).

If you slip at Vno or Vne you might achieve a faster descent rate,
but frankly I wouldn't care to try.

> and I  know I'll probably spend just a few seconds transitioning from 
> Vne or Vno to Vfe.

This is also a faulty premise (based on flight tests).  Certainly
false in many slicker planes.

> I'll be out of my plane *way* ahead of you.

I don't think so.

Snowbird


