B52-yasim readme

2003/05/11 Lee Elliott.

See the notes in the

  Aircraft-yasim/b52-yasim.xml

file for some info and limitations about the fdm.

First of all, this shouldn't be regarded as an accurate represntation
of a b52 - it's based on real numbers etc, where I could find them but
there's a lot of guess work incorprated.

This model tries to emulate a B52-F but I couldn't figure out a good
way to simulate the wet-thrust without affecting all the other engine
charateristics.  As a result, on take-off, it's more or less equivilent
to a B/C model but at the weight of a fully fueled up 'F' model.

'Reluctantly' might be another way of putting it;)

Pick a long, level runway with no high obstacles near the flight-line
(B-F models needed >10000 ft to clear a 50 ft obstacle), preferably with
no cross-winds;)

From what I found, the flaps have only two positions - fully retracted
and fully extended (35 degrees), so fully extend the flaps - I've set them
to operate slowly to allow some time to adjust the trim when they're
retracted.

Set the elevator trim to -0.07 and apply full power.

At sea level, the aircraft should fly off the runway at about 136-137 kt,
possibly with a little skip and a hop, and ascend to about 100 ft and
then more slowly start to climb, if a little unsteadily.  It'll actually
loose and gain a little speed as it climbs, and may even loose a little
altitude at times.  You can retract the gear once the slow climb
has started.

Alternatively, you should be able to just use the autopilot after setting
a suitable altitude.

Eventually, when you've got about 500-600 ft beneath you, you can
retract the flaps, which should be done in one go.  As the flaps
retract, you will need to bring/trim the nose up to maintain altitude as
the aircraft picks up speed.

As I've mentioned in the yasim file, the b52 speed appears to be limited
more by flutter than power - you shouldn't exceed 351 kt at sea-level.

The approach is very shallow and the exact settings will depend upon how
much fuel is left.  I recommend using the autopilot to get the aircraft
down and level at about 1000 ft agl(Tip: Set the autopilot max descent rate
to <= 1000ft instead of it's default 4000ft.  Also, set the autopilot
max-roll to <= 20 deg when the speed's below 220 kt), at the same time
reducing speed to about 180kt.  Dropping the gear doesn't make much
difference but extending the flaps certainly does.  As with retraction,
the flaps should be fully extended in one step.  As the flaps start to
extend the a/c pitch will change quite dramatically and the speed will
quickly drop.

If you're still using the autopilot to maintain altitude all you have to
worry about is maintaining speed:) - don't let it drop below 120 kias -
between 125/130 - 120 seems about right.  Once either you, or the
autopilot, has re-trimmed for level flight, punch out the autopilot, if
engaged, and reduce the elevator trim a few 'notches'.  The a/c should
slowly start to descend and start picking up speed - ease off on the
throttle to keep it below 130 kias.

You'll probably have to make single step adjustments to both the elevator
trim and throttle to get the a/c down in the right place - it's pretty
difficult to judge with such a shallow glide-slope.

I strongly reccommend using the hud energy worm but currently this has to
be enabled by editing the default hud ladder file:
 FlightGear/Huds/Instruments/Default/hudladder.xml
and change the bool value to true.

I currently also have to make an edit to the hud_ladr.cxx source file
to make it work but hopefully this will soon be fixed.

I have also noticed some strange behaviour by engine No. 2. when I
operate the throttles from my joystick - if I slowly reduce power to 0
using the joystick control as engine No. 2. gets near to it's stop it
jumps back up to 50%.  The other seven engines are fine and No. 2. responds
to the keyboard ok.  I haven't yet been able to indentify the cause of this.

It's important to note that I'm not a pilot, have never flown a B-52 and
don't know the actual procedures for getting one down - what I've said
above has just worked for me when trying to land this particular fdm:)

LeeE 2003/05/11
