For Real Pilots

[33Vortex]

Originally posted by Straiga
Airliners fly the same way WWII fighters fly it the same princyple.
Main wing produces lift upward and the horizontal stab produces lift downward to balance forces in the airplane.

I know that, but think I misinterpreted the term 'lift downward', the correct term would be 'negative lift'. If you look at the design of some bombers, and heavy lifters, they have a tailplane that produce lift to carry the weight of the tail. That is not the case with fast, maneuverable fighters.

[jigsaw]

My understanding is that if you lose the tail, you're going to lose the downward lift ("negative lift" is an oxymoron) and the nose will drop. Past that, my "theory" would be a torque roll. Given enough altitude you'd exceeed Vne, where parts of the plane might begin to depart the airframe.

My understanding of "rigging" was the same as Cobra412s. I've only heard it in reference to tweaking bolts, cables, etc. before now.

[Straiga]

Vortex33,

 Since I have been flying airplanes civialian and military, and I have even heard Nasa discribe horzontal tail plane lift. The horizontal tail plane is an inverted wing. The main wing or horizontal stabiliator dosent know its upside down or not, they  produces lift do they not.

As for heavy airplanes the tail produces lift downward as the same for fighters, an airplane is an airplane. The DC -10-30 I flew with a 500,000 Lbs takeoff weight, created lift downward on the horizontal stab it has an inverted wing(horzontal stab) like all other airplanes. The C-5B is the same way as in a B-747, B-52, B-1B, P-47, Me-109, B-17.

If you live close to an air force base or major airport and and see a big airplane look close at the horizontal stab you can see the leading edge of the tail plane pointing down for trim takeoff. Even at the gate you can see the tail plane leading edge pointing down, a positive inverted angle of attack at 0 trim.

Negative lift or negative angle of attack means decreasing lift or decreasing angle on attack.

If I pick up a chair I would be lifting it. If I was hanging from the cieling and pick up the chair I would be lifting it.

Straiga

[Crumpp]

Trimmable Stabilizer

For example, without the moving stabilizer, and with an elevator that moves 10 degrees up and down, if the pilot must hold five degrees of elevator position for level flight, then there is only five more degrees of elevator available in that direction. With the movable stabilizer, the elevator should always be faired when properly trimmed, so full travel is available in either direction.

http://www.avweb.com/news/columns/182097-1.html


Great thread.  I think your absolutely right Straiga.  

Did any other planes in WWII have a trimmable stabilizer?

Crumpp

[Casca]

Originally posted by Crumpp
http://www.avweb.com/news/columns/182097-1.html


Great thread.  I think your absolutely right Straiga.  

Did any other planes in WWII have a trimmable stabilizer?

Crumpp

I'm no WW II airplane expert but the L-4A did (military variant of the J3 Cub) and it doesn't get much simpler than that.  Doubt we will see it in AH.  It would be a long flight with ten of them to take a base.

[33Vortex]

Originally posted by Straiga
Vortex33,

 Since I have been flying airplanes civialian and military, and I have even heard Nasa discribe horzontal tail plane lift. The horizontal tail plane is an inverted wing. The main wing or horizontal stabiliator dosent know its upside down or not, they  produces lift do they not.

As for heavy airplanes the tail produces lift downward as the same for fighters, an airplane is an airplane. The DC -10-30 I flew with a 500,000 Lbs takeoff weight, created lift downward on the horizontal stab it has an inverted wing(horzontal stab) like all other airplanes. The C-5B is the same way as in a B-747, B-52, B-1B, P-47, Me-109, B-17.

If you live close to an air force base or major airport and and see a big airplane look close at the horizontal stab you can see the leading edge of the tail plane pointing down for trim takeoff. Even at the gate you can see the tail plane leading edge pointing down, a positive inverted angle of attack at 0 trim.

Negative lift or negative angle of attack means decreasing lift or decreasing angle on attack.

If I pick up a chair I would be lifting it. If I was hanging from the cieling and pick up the chair I would be lifting it.

Straiga

Doh, I'm not arguing with you, was just confused by the way you worded it. Lift is lift, negative or positive, usually referred to as lift or negative lift. You worded it differently and I interpreted it wrong. I don't blame you for a typo but if you look at some of the old bombers, the A-20 for example, the stab is built with the same, or close to the same, AoA as the main wing. Modern planes don't have that design. Like you say the trimmable tailplane is a common feature today.

[jigsaw]

Originally posted by 33Vortex
... the A-20 for example, the stab is built with the same, or close to the same, AoA as the main wing. Modern planes don't have that design.

Now you've got me confused. Are you talking about the Angle of Incidence or Angle of Attack?

[rshubert]

Originally posted by Straiga
Constant speed props. In AHII if you set the prop RPM to set rpm setting say 2400 and dived to increase speed from 100 to 300 mph, the prop rpm will speed up. This should not happen. it should stay at 2400 RPMhttp://www.allstar.fiu.edu/aero/flight63.htm

I also have been talking about countering torque roll with rudder and airplane rigging. Read this.
http://www.allstar.fiu.edu/aero/flight13.htm

Straiga

Although I agree with you about the pitch-down vs pitch-up issue, I have experienced prop overspeed.  It was in a Citabria that had been modified with a constant speed prop.  Nosing over with the prop set at low RPM would, after a while, result in increasing prop RPM.  I believe that it was caused by the engine being "driven" by the prop at maximum pitch.  Once you hit the wall, where the prop can't adjust any more, the engine will unload and speed up.

I think.



shubie

<300 hours, all in C-172, C-182, C-177, t-6, and Citabrias, all VFR, all fun.
Right seat time in a King Air doesn't count, does it?

[33Vortex]

Originally posted by jigsaw
Now you've got me confused. Are you talking about the Angle of Incidence or Angle of Attack?

Sorry, angle of incidence, relative the fuselage centerline.

[rshubert]

Originally posted by Cobra412
Straiga when you say "rigging" it means something completely different to me or so it seems.  The F-15 needs little to no trim also.  Granted I'm assuming your speaking of propellor driven opposed to turbine driven.  

Rigging to me is actually turning out a locknut and turning out the actual control rod itself for the control surfaces.  From what I'm getting now your talking about actually building the airframe itself so it opposes yawing when in unaccelerated flight.

Oh yes indeed they do!  the vertical stabilizer on a prop single usually has an angle built into it to offset yaw at cruising speed.  Only a couple of degrees, iirc, but it is there.

Twins don't have it, nor do turbojets or turbofans.

[Casca]

There are a lot of questions in aviation that will probably never be completely resolved among pilots.  One example is the downwind turn (my opinion is that it exists but is not a factor during normal operations).  Another is whether it is better to wheel land or three point a conventional gear aircraft in a cross wind (my opinion: wheel land but it depends on the airplane).  Threads on topics like these could probably yield a huge amount of eloquent and reasoned posts arguing the issue from both sides while a unanamous consensus remained elusive.

The subject of this thread is not one of these questions.  It is settled theoretically and empirically.  When the horizontal stabilizer departs a normally loaded conventional aircraft in the normal flight envelope it pitches down violently for reasons that have been stated previous posts.  It is not even debatable.  That is what happens.  If the speed at which this occurs is appreciably above Va (manuvering speed) the loss of the horizontal stabilizer is frequently followed by in-flight breakup.

I spend a lot of time in AH looking at the sky floating down backwards.  At that point I am usually thinking "I hope the b****rd flys down to look so I can nail him." (never happend yet, sigh).  I never spend any time thinking "Ya know if this had been a real airplane it would'nt be exactly like this."

I think the flight modeling in this game is just incredible and merely see it as one of the little quirks of the game.

CFII, CFIG, AGI, A&P, IA
AS Aviation Maintenance
BS Aviation Technology
MS Aviation Safety
Adjunct Professor, Aviation (used to be Assistant Prof.) Central Missouri State University, Warrensburg MO
7000 hrs.  Mostly in crop dusters.

[hitech]

We all know that the horizontal stab creates lift downward to balance the plane in flight

This statement is incorect straiga. If you do a search it has been discused before. Planes can be perfectly stable with the horizontal stab producing up or down force.


Also your assumption that flaps always produce a nose down pitching moment is also incorect. They can produce a nose up or nose down pitching moment.

And finaly pilots are not the best people to ask this type of question .Most pilots only have a very fundemental understanding of stablity and control. And asumptions that they were taught for a basic understanding apply only in the "general case" but not always to specific cases.

HiTech

[Angus]

From HiTech:
"Planes can be perfectly stable with the horizontal stab producing up or down force. "
So, its the Center of lift that decides which force you would need the stabilizer to do right?

Anyway, say your tail gets shot off in a 45 degrees upwards turn,- if the prop keeps running, what force is there to pitch you down?

However, losing the verical stab should lead you to rotate, and end up somewhere??

[icemaw]

Try this test of the nose pitch up. Buy a balsa wood glider. Assemble and fly note results. Then remove tail and fly again note results. Post back with findings.

[hitech]

Anyway, say your tail gets shot off in a 45 degrees upwards turn,- if the prop keeps running, what force is there to pitch you down?

It all depends on the Wing CL combined with the tail CL, If after removing the lift from the tail, The CL of the remaining componets is ahead of the CG the plane will pich up. If it is Behind the CG it will pitch down. The force in either case is the lift generated by the wing.

HiTech