Mxsmanic
Usenet Poster
mxsmanic@gmail.com
Posted on:
Nov 15, 2007, 12:48 AM
Post #20 of 24
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Scott Morris writes:
> A little update to the group here:
>
> I took the default 747 up for a spin last night and noticed a few things:
>
> 1) Fully loaded and fueled, with gear and flaps up, I'm getting AT MOST 5-7
> degrees pitch up.
> 2) If I cut the payload to 340 Lbs (assuming a co-pilot and me) and 1/2
> fuel, I'm getting 3 degrees nose up.
> 3) Speed seems to make no difference whatsoever, neither does altitude (I
> flew at 30000 Ft).
>
> It would seem that payload and fuel play a HUGE part as to whether the 747
> flies straight and level. The only way that I could see this bird flying
> truly straight and level aould be if I had no fuel on board, so if I was
> simulating a transatlantic flight, then theoretically, she shoud. fly
> straight and level towards the end of the flight.
I tried the same experiments with the PMDG 747-400, which is much more finicky
about accuracy than the default aircraft.
With a fully loaded aircraft (602.4 tons AUW) in stable cruise at FL300 and
Mach .908 (redline), I have less than one degree of nose-up pitch; the
aircraft is essentially level.
At FL330, I had about one degree of nose-up in cruise, again at redline.
Slowing to Mach .844, a much more typical and economical cruise speed, I had
about 2.3 degrees nose-up at FL330, just like the real thing. Roughly the
same result at FL300.
At the minmum maneuvering speed of Mach .617 in this configuration, at FL300,
I was able to get 5 degrees of nose-up pitch. But in real life you normally
would never fly so slowly.
So yes, speed makes a difference. So does altitude and aircraft load. And if
a pilot is getting 5-8 degrees of nose-up in level flight, something is wrong.
I got 8 degrees _in the climb_, but not in level flight at any safe speed.
Out of curiosity, I slowed to the minmimum speed for FL300 with this load,
about M.536. I got just slightly less than 8 degrees of nose-up, and the
aircraft was unstable.
The PMDG aircraft is a lot more accurate than the default. However, I can
image that the default might be pretty accurate, too, and perhaps many sim
pilots are just doing something wrong, such as flying with too heavy a load,
or flying too slowly, etc.
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)))))