Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Wed, 30 Oct 2002 14:59:17 -0500
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 originator="Paul Davis <pdavis@pdavis.bmc.com>"
From: "Paul Davis" <pdavis@bmc.com>
Reply-to: "Paul Davis" <pdavis@bmc.com>
Subject: Re: [LML] Re: EngineAir 
In-Reply-To: Your message of "Wed, 30 Oct 2002 12:53:33 EST."
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>>>>> On Wed, 30 Oct 2002, "Hamid" == Hamid A. Wasti wrote:

  Hamid> This is a genuine question from someone who has been
  Hamid> considering moving from singles to twins.  Isn't the whole
  Hamid> purpose of having a twin is that if an engine fails it is not
  Hamid> a major event?

I'm no expert (only about 10 hours of multi time and no rating), but
I recall reading that an engine failure in a twin is more likely
to result in fatalities than an engine failure in a single.  For
many pilots the decision to go multi probably has more to do with
performance (speed, climb, payload) than safety.  Guess redundancy 
doesn't always equate to safety.

>>>>> On Wed, 30 Oct 2002, "Hamid" == Hamid A. Wasti wrote:

  Hamid> This is not the first time I have heard the statement "...an
  Hamid> engine failed and caused the accident" Why is that such a
  Hamid> common occurrence?

Twins are usually heavier, more complex and with higher stall speeds
to begin with.  When you add the drag of the dead engine (even
feathered) with the asymmetric thrust from the running engine --
particularly if the dead engine is the "critical" engine (i.e. the
running engine's prop is ascending inboard and descending outboard
thus producing a center of thrust outboard of the engine at positive
angles of attack) -- it's frighteningly easy to encounter a vmc-roll
(think snap-roll) into the dead engine.  I did this once -- *once*
-- in a Grumman Cougar (Fletcher Aviation for those in the Houston
area).  I don't know who was more wide-eyed, me or the instructor.
From his reaction I gathered that this is not something he normally
allows.  He'd told me to slow fly the airplane and when he failed the
(critical) engine my tiny little brain didn't have "airspeed" early
enough in the "list of things to do/check" so I didn't unload the
airplane quickly enough.  All of a sudden we were at something over
90 degrees of bank with the nose dropping like a pendulum and the
windscreen filling up with Terra all-too Firma.  All things 
considered I'd just as soon not try that again.  Kind of like our 
earlier discussion about deep stalls in aircraft of unknown spin 
recoverability I'd rather not let a twin get below VMC unless the 
wheels are on the ground.  You high-time multi guys out there: is 
actually entering a VMC roll part of the normal training curriculum?

Add in IMC and things would really be interesting.  And I think the
probability of an engine failure in a twin is the square of the
probability in a single.  Not twice as likely, but four times as 
likely.  Yes?

>>>>> On Wed, 30 Oct 2002, "Sky2high" == Sky2high@aol.com wrote:

  Sky2high> Consider a Cessna Skymaster or Adam Aircraft's Carbon-
  Sky2high> Aero.  Both are twins with center-line thrust in a
  Sky2high> pull-push configuration.  There is no bad characteristic
  Sky2high> when one engine stops - the critical engine is the one
  Sky2high> that is still running.

I don't think the accident data support this -- at least not for
the Skymaster.  I've heard anecdotes about pilots failing to even
realize the rear engine had a problem -- particularly on takeoff.
Whatever the reason IIRC the Skymaster does NOT have a better
single-engine outcome record than other comparable "traditional"
twins.

Certainly seems counter-intuitive though.

-------------------
Si monumentum requiris circumspice (epitaph in St. Paul's Cathedral)
If you seek a monument, look around