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Re: [OM] Unusual aircraft

Subject: Re: [OM] Unusual aircraft
From: ChrisB <ftog@xxxxxxxxxxxxxx>
Date: Sun, 28 Dec 2014 11:19:42 +0000
Although I am almost certain that you were already aware of this, Moose, the 
acceleration of the engine is not the same as the acceleration of the machine 
that it’s pushing along.  The poorer acceleration of early jet-propelled 
aircraft would have been due to their lower thrust-to-weight ratio compared 
with contemporary propeller-driven aircraft.

In addition, they had not yet worked out that straight wings were inimical to 
the higher air speeds of which jet-propelled would become capable.  It’s 
something to do with the compressibility of air at air speeds above 300kts: 
sweeping back the wing reduces the increase in drag with speed.

Another problem with jet fighters at their introduction, I gather, was that 
they had lower manoeuvrability, perhaps because they were heavier aircraft with 
similar lifting area.  That is they had a higher wing loading with the 
attendant limitation on agility.

In addition (I’ve just remembered) engine control was rudimentary, meaning that 
it was easy to over-fuel the engine or to reduce the airflow below that 
required for efficient combustion.  This would lead to engine stall or 
stagnation and loss of thrust – temporarily or permanently.  But that problem 
lasted for many years.  I’ve been in a Jaguar in which the pilot (not me) tried 
to select reheat at too high an altitude, resulting in machine-gun reports from 
the intake.  I have also been in a F14 which was powered by the horrible old 
engines; on entering consecutive turns turn each engine managed to stall.  The 
pilot (again, not me) managed to recover the first stall but not the second.  
We returned to Miramar on one horrible little engine . . .

Chris

> On 27 Dec 14, at 21:40, Moose <olymoose@xxxxxxxxx> wrote:
> 
> On 12/27/2014 7:57 AM, ChrisB wrote:
>> Yes, the Jet Provost Mk 3 had a similar problem.  The idle-to-full power 
>> acceleration could take 16 seconds.
> 
> For completely unrelated reasons, what appeared to me to be, and turned out 
> to be, inaccurate historical information in a novelistic memoir, I searched 
> info about the earliest jet fighters.
> 
> In addition to initial reliability and longevity engine problems that limited 
> their actual use, their very slow acceleration and only moderately greater 
> top speeds made them vulnerable to the latest piston engined, propeller 
> driven fighters.

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