Energy bleed

[miko2d]

 I am no pilot and all my flying experience is 45 minutes in a T-6 trainer. That one I really put throught its paces in unbalanced flight and turns and it did lose energy at a fair rate. It was not as powerfull as the fighters but on the other hand it was very light - no armor, weapons, ammo, high-alt equipment, etc. So it's power/weight ratio might have been close. No matter.

 As engineer I think the following info important when estimating the FM accuracy.

 I encountered several reports of experiments  done on various planes (Spits, Corsairs and german planes) directed towards improving the performance of the existing model without significant modifications. They usually referred to it as streamlining.
 I do not remember the exact nimbers, but such a simple thing as changing a paint of a Spitfire to the different kind and making sure all the panels/openings fitted close with minimal gaps yielded an increase of the top speed several MPH.
 The addition of the streamlined bulges over the cannons on german planes gave even more significant increase.
 Now if such a trivial change as different paint reducing the air friction can add a few MPH, imagine what flying sidewise would do to your performance! Compare a crossection of the trimmed plane to a plane at any angle of attack, factor in that the resulting crossection, unlike the front one is anything but aerodynamic.
 Want to know what area is added to the crossection at a gentle AOA of only 10 degrees - SIN(10) = 0.17
 That is 17% of the whole surface of the wings, body and the horisontal stabilizer. Look up the numbers if you want.

 I know that when I stick just the palm of my hand out of my car at 70MPH, the force pushing it is greater then I use to push my car when on neutral (I have Honda Civic, it is pretty light). Imagine 300-450MPH (enough air resistance to rip off airplane gear) and you stick the area equivalent of the whole Honda Civic out of the window!

 You would lose that energy fast. If anything, all the flight sims undermodel that aspect of flight.

 I saw a post here where somebody complained that he could not do a level 360 degree turn in a P51 without losing altitude, starting at any speed and climing it's energy retention was not realistic. Even P38 could not do that (according to the pilot reports). In P51 if you follow the bogey into more then 45 degree turn, you are killing yourself.

 Good energy retention means that when you come out of a dive with lots of speed and start flying perfectly level and trimmed to zero AOA and zero slip, you keep that speed longer because of your clean aerodynamic crossection and weight.
 When you are flying sidewise or belly first, there is no energy retention to speak of.

Good job, HTC!

miko--

[Toad]

Well, a mere PT-19 at "normal" operating gross weight (nearly full tanks, 2 pilots) with a 200 HP Ranger will do a level, 60 degree bank turn (2G's) at a constant airspeed (about 90 kts) as long as you want to do one or until you run out of gas, whichever comes first. It doesn't even take full throttle.

I haven't run the AH planes through my basic "test flight" profile yet, so I won't comment on those characteristics.

I would be simply AMAZED (Astounded? Incredulous? <g> ) however, if a real P-51 can't do as well as a PT-19. Thus, I'd expect the AH modeling to show similar results in a similar turn.

[-blk--]

  I think he was talking about a 360 with 90 degrees of bank.  Heck, 8er and 9er (Cessna 150s I fly) can steep turn at 60 degrees all day long should I please...

  However, once you get to a 90 degree bank, you need to use the rudder to point the nose above the horizon in order to maintain altitude.  That is mighty tough to do.  

  I've never flown an aircraft that could do 90 degree banked level turns.  And I tried it in the T-28C (which has lower power/wing loading than a Stang).  But, who needs to do them at 90 degrees?  Just roll to about 85 degrees, then keep pulling back just enough to keep the nose above the horizon/maintain altitude...

blk  AT

[Brick]

Hey Toad, is the PT-19 the "Yellow Peril"?

-Andy

[Toad]

Yes, 90 degrees of bank and level flight is an entirely different story.

Still, if you're looking for a quick check of programming, a level, 60 degree bank turn should show 2 G's on the g-meter and I'd think that any of these fighters could maintain it indefinitely without using full throttle, given a "basic" loadout. I don't have the AFM for these, but I suspect hanging a pair of 1000 lb bombs under the wings might be quite a different story.

Now, in performing this check, it's up to _you_ to maintain a steady 60 degree bank and a 2G pull without horsing the stick around. Don't suspect "bad programming" if you're pumping the stick from 1 to 3 G's for a 2G average. You're changing the drag equation pretty dramatically there.

Of course, if the g-meter programming is off...the whole test is out the window <g>.


Nah, the Stearman is the "yellow peril".

The PT-19(and -26 and -23) were Fairchilds.

The -19 is an open cockpit, low wing monoplane with an inverted overhead cam 440 cubic inch 6 (Ranger, designed/built by Fairchild). The -26 is the same plane with a canopy, requested by the Canadians when winter came on and their initial orders of-19's proved a bit chilly. The -23 is a -19 with a Continental 220 radial on the front (looks like a 19 that taxied into a brick wall <g> ); they built this when there were doubts (proved unfounded) that they wouldn't be able to build Rangers fast enough.

The -19 is simply a joy to fly for too many reasons to list. It's probably the best trainer I've ever flown for teaching a kid the basics without letting him hurt himself. I got it for that reason and my two boys are well established as students in this old taildragger.

Interestingly, while the Stearman is remembered as "the" US trainer, more Fairchilds (all variants) were built than Stearmans...but it was real close.

Sorry for the history lesson...but I really like this old bird.

[This message has been edited by Toad (edited 10-06-1999).]

[-blk--]

  You own a Cornell Toad?  Awesome!  My Grandfather was an instructor in the PT-19's during the war...

  He's just as complimentary about them as you are...

blk  AT

[Brick]

Toad said:
Nah, the Stearman is the "yellow peril".
The PT-19(and -26 and -23) were Fairchilds.

Thanks!    Man, I gotta start increasing my WWII a/c archive.  There's a ton 'o cool stuff out there.

-Andy

[Toad]

BLK:

Actually, BLK, there are 3 in my family. My brother and I have -19's and my father has a -26,

Dad started in -19's in '42. We all love them. Just a fun old airplane.

[ft]

I'd really enjoy seeing a pilot pull off even a 30 or 60 degree level turn banked 90 degrees - leave alone a level 360.

That'd call for some mighty fine knife-edge flying(*) skills!

(*) Flying with a 90 degree bank, using the body of the aircraft and the fin to provide lift - it can be done in AH, most impressive.

Cheers,
   /ft

[jedi]

You guys are leaving out the critical element here--G loading in the turn.  ANY plane can do a level, 60-degree banked turn indefinitely, so long as you are doing it at a constant speed which you can sustain.  If you try to decrease your turning radius by pulling G, the induced drag will cause your airspeed to decay, which will decrease your turn performance if you're below corner velocity.  

Can a C-130 outturn an F-15?  At 150 knots it can    Can a PT-19 outturn a Mustang?  At 80 knots, you better believe it.

As for level, 90-degree banked turns, that's a physical impossibility.  It requires INFINITE G, because NO lift is directed away from the ground.  (Some modern acro planes may generate enough lift from their fuselage and rudder to do it, but not a WW2 warbird).  WW2 planes simply didn't have enough excess thrust to do hi-G turns indefinitely.  Even modern jets can't do it for long.

Which is not to say that these planes can't fight an extended turning battle--just that the speeds, turn radii, and G-loadings are going to be a lot lower than you might think, especially at altitude.

--jedi

[Toad]

Very good point, Jedi.

G loading is key in energy bleed.

I'd think all these fighters would do the old standard "60 degree bank, 2G, level turn" indefinitely with a standard "combat" loadout. Otherwise, they'd be seriously underpowered and probably wouldn't have been built <g>.

[jedi]

I agree, and to be honest, I haven't gone out and just tested the planes in normal manuevers to see if they can do normal things.  They don't SEEM to be stalling too early in combat manuevering to me, but I haven't done much combat manuevering in the last few years  

As for "combat loading," if you mean loading bombs and rockets on, I wouldn't be too sure of being able to pull many Gs.  Even the F-16 is severely G-limited when hauling iron on the hard points.  I'd be surprised if a Mustang could pull more than 3 or 4 with drop tanks or bombs loaded, but I would think the 2G, 60-degree banked level turn would still be possible.

--jedi

[This message has been edited by jedi (edited 10-08-1999).]