Aerodynamics: Is mushing a myth?

[starch]

I recently wrote a precis on maximum all-up weight operations and came across an interesting aeroD question.

Some textbooks claim that turn radius is dependent on airspeed and bank angle and nothing else, wihlst in other formulae the weight (or thurst-weight ratio is included).

Does a heavy aircraft mush more than an empty one or is it purely psychological?


Thanks,
Starch

(PS: I am aware of the limitation in AoB due to the added weight, which would lead to a larger turn radius, but that is not the issue.)

[L Peacock]

Higher AOA for given g with increasing mass (therefore more drag/ thrust required etc) Don't think bank angle is affected (assuming level flight <90AOB). Bet I'm wrong though!

[Hummingfrog]

I thought that the mass of an object was a constant where ever you are in the universe it is the weight that changes:confused:

HF

[Onan the Clumsy]

[:8]

...at sub light speeds perhaps, but not at super light speeds


personally, I think most of 'aerodynamics is a myth and remain unconvinced about bernouli and lift.


[/:8]

[Unmissable]

Beam me up Scottie.

[BEagle]

In a steady turn, Radius of turn R = TAS squared/(g x Tan AoB). Whether in a Tutor or a C-17. Always has done, always will do! And that's g as in 32 ft/sec/sec or 9.81 m/sec/sec, of course.

A large aeroplane normally rolls a lot slower than a small one (except, perhaps for das verdammte Teutor) - so the time taken to roll from wings level to the turn AoB and also the time taken to roll out to wings level again from the turn AoB will take longer in a biggie, meaning that the total time from starting to finishing the turn is correspondingly longer. The 'g' force in a steady banked turn is equal to Sec AoB - so it'd be 2g in a Tutor at 60 deg AoB and 2g in a Vulcan at 60 deg AoB...

WTF is 'mush' - something you say to huskies? Or what peasants do to peas?

[Zoom]

Quite right, Beagle, although all this 'large aeroplane' stuff is well beyond me..... :p . Don't forget the effect that altitude has.... umm..... IAS.... err..... TAS..... (scrabbles around for Cranners notes - still have those, BTW).

I have a chart somewhere which makes light work of calculating radii, etc. If I can find it I shall let you have a copy, starch.

[BEagle]

Nomograms are for gnomes....

Use TAS in nm/min and 'g' as 19.065 nm/min/min. Then radius of turn (in nm ) = TAS in mi/min squared/ (19.065 x tan AoB).

That's what I used for all the ATP-56A turn range values - by programmes I wrote in Basic on the old sqn BBC Master computer!

[Zoom]

A squadron computer, Beagle? What a flagrant waste of taxpayer's money. Standby while I Roneo you a half dozen of my handy charts!! Now where's that stencil......?

[BEagle]

Our boss at the time was very 'into' computers.......

Which was fun, because it used to confuse Plod - who viewed computers as devices purposely-designed to undermine authority and steal state secrets.....

I don't think they'd ever seen a computer used for iterative calculations.

[MrBernoulli]

A plod thinks a computer is for playing Solitaire on! Dipsticks.

[normally right blank]

Is mushing a myth?

“Mushing” is/was a reality on some aircraft. (I’ve seen it myself! ;) ).

From “North American F-100 Super Sabre. T.O.1F/TF-100D/F-1 1/2. Fact Manual” (ISBN 87-987847-0-6) (in Danish): Two references to “mushing”.

(Pilots’ impressions) “... Looking at the “Super Dog” from a distance, it was hard to understand that she possessed characteristics, that only a few chosen were privileged to discuss in the semi-dark protecting atmosphere of the bar. Sabre Dance, adverse yaw, “mushing“, compressor stall, control stiffening, flat spin, P.I.O., drag chute failure, too small brakes etc.. A Hunter pilot converting to F-100’s thought to himself: “What’s going on here? Why don’t they stop this uneven fight?”...”

“... Air-to-ground the F-100 required a good craftsman. Dive angle and speed had to be spot on. Otherwise you didn’t hit. Due to the aircraft’s large mass, you had to be very exact on your speed during pull up and roll in for an attack. If you pulled too hard during roll in, you could end up with too little airspeed to pull out of the dive. When you pulled the stick the aircraft rotated well enough, but the aircraft just continued “mushing” in the original direction. That took precious, sometimes fatal seconds, before the vector changed and the aircraft started to pull out of the dive.....”

[maximo ping]

Standard QFI spiel to UAS students on subject of aerodynamics; "Any aeronautical engineering students here? Excellent..., please bear in mind that what I am about to teach may or may not bear any relation to how aircraft actually fly, but it is how the RAF chooses to explain the phenomenon and should therefore be learnt rather than viewed as a topic for discussion..."
:ok:

[ACW599]

Wasn't one of the problems of the Swift supposed to be 'mushing' and very poor turning performance? I also seem to recall reading that applying up-elevator changed its attitude but had little effect on its velocity vector. Why would this be? Are there factors that affect the turning performance of an aircraft other than those discussed so far?

[normally right blank]

What I did see was in the spring of 73. Harriers (1 SQN?) jumping out of a woodshrouded threshold of RWY 04. Then high and low speed passes and touch & goes on the grass rwy. (Burn marks for the rest of the Summer).
But before that the "locals" demonstrated: Drakens and F-100's attacking. The Drakens kept to the regulation "300 feet". One of the Super Dogs (727 SQN) most certainly did not and "mushed" vertically more or less directly from 1.000 feet around the GCA to point right at us (the "public"). Nice pull up over our heads and a "victory"? roll. After landing the tank pylons of said F-100 were apparently "strechted" a bit! I've never, before or since, stared right into the intake of a speeding Super Sabre ten feet off the ground.