I'm referring to the named pilot who experienced the same difficulty and apparently climbed until regaining consciousness.
Does it seem likely that full nose down trim and forward stick pressure are used all the time? Lots of drag with that kind setup, exactly what isn't wanted in a race. Or maybe the P-51 is tail heavy and the horizontal stabilizer is a lifting surface, like with the P.180 Avanti?
Beryl fired this volley in news:j5qc6r$5c5$1 @speranza.aioe.org:
That would create parasitic drag, which is just as bad.
There's no way these guys are flying deliberatly "dirty". Hanging all that pitched up/down crap out in the wind is just another form of air brake.
LLoyd
But somehow the Avanti is the fastest turboprop.
That sums it up nicely.
January 2007 Air & Space Smithsonian magazine has an article titled The Physics of Winning.
Author George C. Larson writes - "Most try to relax the airplanes static pitch stability by moving the center of gravity as far aft as possible without making the airplane unsafe in slow flight. This reduces the work the horizontal tail has to do to keep the airplane balanced in turns, and reducing the workload of the tail reduces drag."
Larson says about P-51 Strega pilot Bill Destefani - "His team went to great efforts to remove every last bit of trim pressure that would be exerted at top speed. Even a small surface like a trim tab or a tiny control deflection adds drag."
Quoted from Destefani himself - "The Mustang was a compromise. The engine is set in there with a thrust line of 1 or 1.5 degree upwards. We had to change that. The Mustang also had 1.5-degree kick right on the vertical tail. We make it zero. The stock Mustang at 400 mph will take 6 degrees of left rudder trim to fly straight, and they tweaked the rudder to help those 18-year-old pilots. You take it out so there's no rudder trim, no wing trying to raise, no aileron trying to rise. We clipped the wings 30 inches, so you have to land it faster. You have less drag, but it's speedier on landing and takeoff."
That would be news to Tupolev.
What, the Bear bomber, or whatever it's called? I recall that's a speedy one alright.
Actually the airliner derived from it. 541.45 mph over a 1000km closed course, 532.6 over 5000 km.
The military versions are supposed to be faster.
At 500 MPH? Of course it need nose down trim.
I'm guessing you kind of skipped over the numbers.
I'm also convinced you are not a flyer.
One little tidbit of information is that with most aircraft you can get a couple of extra knots of speed if you trim the plane up ( the trim tab is set in the neutral position for least drag) and then you apply forward pressure to the yoke. The drag of the trim tab to force the elevator down is eliminated picking up a little more speed. I found that out by playing with the trim on the many long boring flights I've taken.
John
Or reflex your flaps.
Nose down trim relative to what? Cruise?
The Unlimited class racers are optimized for best performance = least drag at ~500 mph. If they need nose down at that speed, the streamlined horizontal stabilizer will provide it. Not some angular pitched up/down crap hanging out in the wind, as Lloyd aptly describes it. So, when optimized for 500 mph, of *course* it needs nose up trim at 200 mph! And it's also draggier than it needs to be at 200 mph, with all the pitched up/down crap hanging out in the wind.
I don't see where any numbers were discussed. Provide some numbers where you feel they're missing.
I am crushed. Read what I posted from the Air & Space Smithsonian article. Pilot Bill Destefani doesn't agree with your understanding of how his P-51 Strega works.
Do you know what would happen if the elevator were rigged for zero trim at 500 mph?
What's the tradeoff?
I assume you mean stabilizer, not elevator. You'd have zero induced drag from the trim tab or elevator. And if you put the Center of Gravity right at the Center of Lift, none from the stabilizer either. Bill Destefani likes all of that, but it's not very safe.
Tell me where you disagree.
1) The airplane is always nose-heavy, of course, even at 500 mph, but as little as Bill feels is necessary for safety. 2) The tail surfaces need to produce some down force to keep the nose up, even at 500 mph. 3) Why are you pushing the stick forward to hold the nose down at 500 mph? Only because the elevator is properly trimmed for 200 mph. 4) Trim the elevator for 500 mph and you won't have to push the stick. 5) Rig the stabilizer for 500 mph and you won't have to push the stick, AND you won't have the elevator or trim tab jutting out into the airstream. Everything is lined up nicely.Less efficiency at the speeds where most airplanes spend most of their time, cruising along at ~70% power.
How about a 200 MPH landing speed?
Richard fired this volley in news:ccWdnRYSPO_s3xzTnZ2dnUVZ snipped-for-privacy@earthlink.com:
Yeah... do you? Although I have lots of hour PIC, I've never flown a full-scale pylon racer. But (just like the guy in a Holiday Inn Express commercial) I've flown model pylon racers. Real (not scale) speeds of
200+ mph. They are not "toy" airplanes, they're real airplanes made smaller. They behave to aerodynamics just like big ones (although they tend to leave less wake turbulence).We trim 'em out for max speed. Then we honk on the stick pretty hard at low speeds, just to keep the nose up. So what?
The ONLY reason these full-scale racing guys want to land for, at all, is so they can gas up and do it again! So long as the aircraft handling is survivably safe at landing and takeoff speeds, all they're concerned with is how clean they can make it at full speed.
Since one _can_ adjust one's approach speed, there need not be any compromises.
LLoyd
Do you have any idea of the flight characteristics of a wing with the CG and CL in the same spot?
If the plane is nose heavy at 500 MPH what do you think it is going to be like at 100 MPH and the much lower lift you have there.
With the CG and CL at the same point you have an extremely unstable aircraft. I thing that the original P-51% figures were in the 20% of cord neighborhood and it had a reputation for being very "twitchy".
One of the basic reasons for having the CG ahead of the CL is so that if you stall the airplane the nose will drop which hopefully, will allow you to recover.
If you trim an aircraft for hands off level flight at 500 mph you are going to be extremely nose heavy at take off and landing speeds and it is going to be very difficult to control the aircraft, if you lose the power at low speed the nose is going to drop very, very quickly. AS Richard pointed out the lift generated by a wing varies considerably with changes in the air speed and consequently the trim, the tendency to dive or climb, must also change.
Yes, that's why I said said it's always nose heavy. I'm attempting to point out that always pushing the nose down on an airplane that's already nose heavy is nonsensical... except I've read that the Blue Angels do trim their jets that way. It helps them keep a steady hand.
Still nose heavy, and trimming the nose up would be a good idea.
I know that. Even before you stall, the nose lowers. This is what's behind the whole reason that pitch controls airspeed, and power controls altitude (another interesting argument).
I know that.
Of course trim needs chsnge. Richard apparently believes that some nose-down is ALWAYS needed, and only the /amount/ of nose-down changes as speed changes.
X-15? What lands at 200 mph?
Are you saying that the Galloping Ghost, or Strega, couldn't be rigged for minimum drag at 500 mph because they'd then have to land at 200?
Note that I never said the Stabilizer produces no nose-down force at 500 mph. I'm only doubting that the Trim Tab/Elevator are doing much work there, at all. Set the Stabilizer to do the work, and lift (downward) comes by way of Angle of Attack. But set the Trim Tab and Elevator to do the work, and lift (downward) comes by way of Camber. And not even a good camber, it's all zig-zagged and creased.
Beryl,
One last try and then I'll go away and leave you alone.
Forget "nose heavy".
Think "pitch", aka deck angle, or preferably, angle of attack.
Within limits of course, angle of attack directly controls the amount of lift generated by the wing. Yes, other parameters are also involved but this angle is what the pilot has control of via the stick.
For straight and level unaccelerated flight, lift equals weight. (thrust equals drag too, but that's another story)
As speed increases _so will lift_, unless something is done to keep that from happening. THAT trick is simply pushing the nose down.
(Airliners often pump fuel forward(!) but that's a bit over the top for light aircraft)
By lowering the nose, the angle of attack is decreased, thereby decreasing the coefficient of lift, and, if done right, maintaining a constant altitude (the level part of straight and level)
Ok?
That's the whole of it.
So...
Quote Of course trim needs chsnge. Richard apparently believes that some nose-down is ALWAYS needed, and only the /amount/ of nose-down changes as speed changes.
So for the discussion of a racer at 500 MPH, Yeah, True, Si, Da...
When landing, no.
The elevator - and the trim tab - do a LOT of work on a race plane at
500mph. And a lot at 200 too.Have something to add? Share your thoughts — no account required.
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