From: waugh@rtpnet05.rtp.dg.com (Matthew Waugh)
Subject: Re: Flying defensively...
Date: Tue, 12 Jan 93 18:52:11 GMT
Organization: Data General Corporation, Research Triangle Park, NC

In article <2629@usna.NAVY.MIL> dfr@usna.navy.mil (PROF D. Rogers (EAS FAC)) writes:
>In article <1993Jan11.170830.4514@dg-rtp.dg.com> waugh@rtpnet05.rtp.dg.com (Matthew Waugh) writes:
>!You cannot argue that you don't fly twins because they are more
>!dangerous than singles, you have to honest, and say you don't fly
>!them because you are poor :-)
>
>Even with the smiley I'll still argue that I don't fly twins because
>they are more dangerous than a good well maintained single. I could
>certainly handle the financial end. However, as an aeronautical
>engineer, I've taken a good look at the performance of the typical
>light twin and don't like either the single engine climb performance
>nor the single engine control characteristics. I think I'd have
>to go to something like a small Citation Jet or a Beech 350 to
>get what I would call reasonable performance from a twin and
>that I can't manage economically.
>
>Then there is the issue of the time to maintain proficiency. Even though I
>am currently flying 150-200 hours/year I don't think that is enough to
>maintain proficiency and also do anything reasonable with the aircraft.

For the sake of this discussion (and that's what it is, because I
really have not studied this, and even if I had I'm not as well
qualified as Prof. Rogers) we'll ignore proficiency. You are
proficient at multi flying, I have waved my wand and made it so :-)

So the discussion is, are twins safer than singles. As I see it
these are some areas to consider:
1. How likely is an engine failure? I got some mail, and heard
   elsewhere, that having 2 engines doesn't make either one of
   them failing any less likely (which makes sense). So you are
   as likely to lose one of your 2 engines in a twin, as you are
   to lose your only engine in a single. You are not more likely
   to lose one of your engines though.
2. Which brings the more important question of when you lose one
   in a twin, how likely are you to crash? Leaving out environmental
   luck (like being over an airport), which would apply just as
   well in a single, what are the advantages of having one turning.
   - Extended glide range, even if it won't climb or maintain
     altitude, a twin will glide a lot further with one working,
     making it less likely you have an off airport landing.
   - It should maintain altitude, so in fact you should be able to
     get to a perfectly good airfield and land.
   Disadvantages:
   - We assumed we were proficient, but even so, losing one on takeoff
     has got to be a very dangerous time, with a crash being at a 
     higher speed. Any other time you lose an engine though, you
     should be OK.

The FAA agrees (so what does that prove) that twins, when flown by 
proficient pilots, are safer, since it won't allow for hire passenger
flights in a single engine aircraft.

To return to proficiency, I would agree that's the killer for low-end
twin flying. I believe that too many twin accidents are the result
of pilots who are not proficient, not that twins are more likely
to crash. Which comes back to a money issue - it costs money to 
remain proficient :-)

Prof. Rogers argument that he doesn't like the single engine climb
characteristics doesn't address the fact that they are a lot better
than the no engine climb characteristics of a single. The control
issue, well, I guess I go back to proficiency, if you are proficient,
in fact even if you are fairly un-proficient, as long as you keep
your speed up, you will descend at a slower rate than a single
with no engine, and thus have more time to plan your accident.

I would argue that even if you follow these rules with respect to
twin flying:
- any engine failure below 1000 feet on departure, pull both
  throttles and land straight ahead.
- any other engine failure, plan a 100fpm descent, and get to the
  best landing field possible.
Conservative rules to say the least, you'll have less accidents
than single engine pilots, but people(*) will die more often when
you have such an accident. Maybe it's thinking like this that makes
twin pilots hit the ground believing they could make it, as opposed
to just accepting an accident, and having the best one possible.

I just don't think you can argue that twins, in general, are less
safe than singles. You might argue that a pilot who was not proficient
is safer in a single than a twin, but that's hardly the fault of
the aircraft - if you want multiple motors, you have to pay the
price (oh no, he's back on money again). If you define safety as
being likely to have an accident. If you define safety as more
likely to die in an accident, well you got me there, I think it's
fairly clear that in a twin, due to higher stall speeds, and
consequently faster crashes, you are more likely to die if you crash.

(*) thats people in the generic sense, a particular person, in general,
can die only once :-)

Mat

Matthew Waugh			waugh@dg-rtp.dg.com
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