prop hanging experiment

[Bozon12]

i read a lot of posts here about ACMs involving hanging on your prop.
so as a newbie (a bit less than 2 months) i tested a few of the AC to see how they handle it. here it is:

method:
1. all AC with 3/4 fuel, no load.
2. level flight at 1KFt, speed 300 mph.
3. full throttle punch WEP.
4. gentle pull (2.5 G) to bring nose up 70-80 deg (90 is very hard to maintain and the plane would actually fly "backwards").
5. hold till stall (requires increasing forward stick pressure in order not to flip).
6. check max alt.
7. repeat 2-3 times for each model, mark best result.

results (high to low order) in Ft:
tempst - 5400
yak u - 5400 (and with style!)
dora - 5300
la7 - 5300
109g10 - 5250
p38 - 5250
p51D - 5200
niki - 5200
190A5 - 5150
Dhog - 5150
spit IX - 5050
109g2 - 5050
p47d - 4750 (?!)
B26 - 4100 (had to try this one   )

estimation on error:
due to the un-scientific nature of this test and significant possible err on initial conditions i would *guess* an error of 100 Ft at a 85% of the probability distribution.
(very amaturistic, but so is this experiment...)

results analization:
the tempst and yak are clearly best at this manuver, with yak crowned as the winner. i was amazed how well it handled till the top, and then simply fell back on his tail for about 150 ft, lowered nose and gained level flight at above 5100 ft!
most AC went out of control at the top, and was quite hard to prevent from falling sideways.
another supprise was the low alt gained by the p47d30. i tried it 3 times to make sure but always with the same result. i thought this should be one of the better - but it might be my lausy flying.
most other fighters where in the same range of 5150 to 5300 which is well within the err to distinguish.
B26 - 4100. very nice for a buff and good for dogfighting a lanc... 8-)

conclusion:
call me when the ruskies put 40 more 20mm shells on the yak. one damn fine plane but just for snipers (need all 120 shells on one target myself   )

see ya around,
Bozon

[gripen]

Interesting, the Tempest is the best but the Jug should be very close, at least as good as the Pony.

gripen

[funkedup]

Neato.

I wonder how the results would change if you dove to 1k, let the speed drop to 400 IAS, then did the test?

[ 08-17-2001: Message edited by: funkedup ]

[Kweassa]

And let's not forget..

 How would the test be at .. say..

 10K, 15K and 20K?

 ..

 300 mph at deck alt... and the N1K2 holds zoom almost as hard as a 109G-10.. wow..

[Westy MOL]

My best in a Yak-9T is 7 kills (two lancs included) in one flight and in a Yak-9U it was 5.
 If you only got one in a Yak-9U then you give up easily  

 Westy

[Bozon12]

i don't give up. i'm just a lausy shot.

i suppose results would be different for 10k 20k, but i don't have the patience to climb there  

and yes. a 400 mph should be interesting.
i'll try that.

Bozon

[ra]

The plane that surprises me is the Dora, it doesn't do too well in the MA.   As far as the Jug v P-51, the Jug only has about 10% less zoom than the P51, that seems OK to me.
Try the same test at 500mph.

ra

[raven 8]

the 109s climb better once they are up high. temp only climbs well low down.:-)


messiah1

[Fester']

the prop has a lot to do with how good hangtime is.

there is a hartzell prop that adds a lot of hangtime to certain aerobatic aircraft but its very expensive.

[Regurge]

Nice test.

In my experience with the jug it actually seems to zoom higher if you pull hard for the first 45 degrees or so. It seems that getting the nose pointed up is more important than conserving E.

If you could manage to do the test with all planes going vertical at the start I think the Jug would come out better, and pull farther ahead the faster you go.

As it is, much of the test is on e-bleed and high speed climb during the pull-up. Not to bash your work of course, I appreciate all tests like this.

[mrfish]

veddy interestink

[Bozon12]

WARNING! READING MIGHT CAUSE A HEADACHE.

So far I've been to lazy to do another experiment, so I've been thinking about it a bit.
the theory is this:

consider the plane as a chunk of mass "m" moving straight up with a pulling force "F" (prop) against garvity "mg" and drag "d".
we'll assume body drag only, neglecting aerodynamic effects (wing tip turbulance, etc.) due to low attack angle in the vertical.
so " d=jx' " where:
x' = velocity (first time derivative of distance)
j = drag constant.

it's an over simplification but i think that's enough to get the idea.  

if a=x" is acceleration, we get:
ma=mx"=F-mg-jx'
which is a diff. equation of the form:  x" + Ax' = B

well, you got the idea. so to save time and key strokes, the solution is:

x=[(F-mg)/j - V](m/j)*exp{-t*(j/m)} + t*(F-mg)/j + H

V = initial speed.
H = constant calibration for initial alt.

if we plot this function we get a sum of an exponent and a line with a single maxima.

results:
1. m/j - we see (as one might expect) that the ratio m/j appears several times. so as for body mass and drag what matters is the ratio.
the higher the better. a drag efficient but relatively light AC would not benefit much of that factor.
BUT, the higher you are, j gets smaller! so high m/j planes should enjoy this.

2. F-mg (negetive value) - how big an engine comparing with weight.
this is a dominant factor, and gets more important as j increases (at low alt).
light strong planes should benefit here (yak as an example?).
this enables them to stay longer almost stopped at the top.
maybe this explanes the yak preformance at the experiment.

3. V - initial speed.
effects the exponent term only (ruled by m/j ratio). so this also work for better m/j planes.

conclusion:
1. high m/j AC makes a good vertical fighter and gets better with alt and speed.
   for some conditions, being loaded with internal fuel might actually help here.
2. Big engine + small plane? advantage at low alt and not too high speeds. (not to mention smoother manuver).
3. the experiment was in bad conditions for the jug. but i still think the result is poor.
4. more testing is needed to verify the above (and of course - we don't have the exact data to apply here).

i'll test that and report.

Bozon
332 Vikings Squad