Throttle back on downwind

Yes.

Because of folklore.

It is.

"Icebound" wrote in news:dusj2i$4u3$ snipped-for-privacy@emma.aioe.org:

I read something about builder using spoilers instead of ailersons just like the real B52. Plane is sensitive to banking maneuvers, when certain attitudes are entered, it cannot recover from that attitude because spoilers, unlike ailerons become ineffective.

Makes no sense to throttle back on a downwind leg. Sure, the groundspeed will be faster downwind than upwind and you might have to turn a bit harder when turning back to upwind, but if the airplane can't handle those stresses, it's better off on the ground. It all amounts to relative wind across the wings, not groundspeed.

The only valid reason I can think of to throttle back on downwind is if you're trying to make a smooth looking flight; in that case then throttling down would make the upwind and downwind legs look the same. If you did this you'd have to be careful of the turn, because you'd have significantly less airspeed then you'd see.

In a full-scale aircraft you may be interested in tracking something on the ground, but if you just want to get from point A to point B you should set the airspeed where you want it and be happy with any tailwind.

All the more reason to maintain airspeed and ignore ground-speed.

I am just a little amazed that a pilot obviously skilled enough to take on such an ambitious aircraft, would think that "throttling back on downwind" is somehow beneficial.

On Fri, 10 Mar 2006 14:12:14 -0500, "Icebound" wrote in :

I think you're right.

It's a shame they didn't have telemetry to help them fly the plane. It shouldn't be hard to establish the normal airspeeds for a model that size if you have a pitot tube and a downlink.

Marty

-- snip --

First, building skill isn't always the same as piloting skill -- I consider myself to be much better at building than piloting.

Second, sometimes the skill necessary to build such an aircraft can be limited to being able to sign your name to a check (or cheque, in this case).

Pilots and builders are two different creatures, as proven by this example.

Ed Cregger

I was reading some post on RCU and those guys were saying the pilot has been banned from flying any more large planes. They were also saying he had crashed everything he has flown. He can build some awesome planes, but it sounds like he is spending most of his time building and getting rusty in the flight department. The Scale Masters used to be a crashfest a few years ago before the team class was introduced. Those guys produce works of art but have a little trouble when the wind picks up or starts to run across the runway.

This problem has been around ever since I began modeling back in the late Fifties. Yes, even in control line.

What gets me is that some of these fellows are really terrific craftsman and are extremely knowledgeable, about everything BUT flying. Normally, you couldn't tell them a thing. They knew it all. Just ask them. Fortunately, many of their aircraft never got more than a foot or two off of the ground, if that.

The ones that really cracked me up were the ones that would show up at the field with a beautiful scale rendition of something in what we would today consider a .90 - 1.20 sized model with a very high wing loading. However, upon closer inspection, we would find a tired old K&B .35 green head engine residing in a perfectly pristine engine compartment.

These models were seldom able to taxi, much less takeoff and fly. I could swear that these fellows actually resented having to put up with a stinky, slimey and loud glow engine that forced the builder to deal with mundane things such as adequate cooling air, muffling and access to the engine's needle valves. This was back in the late Sixties to early Seventies. Things have improved a lot since then - I suppose.

Ed Cregger

Sure they have improved. ;-)

Now its a geared speed 400 and LiPo's.

On 11 Mar 2006 06:38:38 GMT, Michael Burton wrote in :

Poor fellow!

That was a world-class model.

Not many others like it that I know of.

It actually looked to me as though he lost perspective on the plane and banked twice in the same direction. Then, once it was nearly perpendicular, he couldn't right it again.

The claim that he throttled back too much may be what HE thinks is the right explanation. If he's that weak a pilot, his thoughts on the matter may not be an accurate description of what really happened.

I've only met one of the Masters--Charlie Nelson, a.k.a. "Mr. WACO."

He had the cutest little practice bipe that he would haul out of his van--all assembled. He'd fill the tank and walk to the flight line with the plane, his TX, and a glow driver. The little four-stroke was economical enough that he could get two practice flights out of one tank of gas.

He very kindly offered me some pointers on how to do rounder loops with my UltraSport .40.

A fine man and a fine pilot.

He lost TWO of his WACOs at the same Top Gun, I believe. I don't remember the details--only read about the in the mags. My impression is that neither was his fault.

Marty

-snip-

Roll control on both the full scale craft and on that model is via spoilers on the wing tips, which lose effectiveness at low airspeeds. Couple that with the anhedral, and if you let it get to slow and rolled too much it'll go over on it's back.

Apparently this has happened to some of the full-sized ones as well.

I couldn't say if it's because he throttled back or because he didn't keep the nose down. It did look like he burnt up a lot of work quite rapidly, though.

Tim Wescott wrote: > Roll control on both the full scale craft and on that model is via

Right, and in addition, the B52 doesn't have sufficient rudder authority to keep the nose up in extremis.

Perhaps most notably, the 1994 crash at Fairchild AFB:

| Makes no sense to throttle back on a downwind leg. Sure, the | groundspeed will be faster downwind than upwind and you might have to | turn a bit harder when turning back to upwind

Why?

| but if the airplane can't handle those stresses, it's better off on | the ground. It all amounts to relative wind across the wings, not | groundspeed.

True.

However, while most of the differences between flying in wind and in calm air are are strictly perception related (i.e. your plane *looks* like it's going faster downwind) there are some real differences, mostly related to a the wind gradient found near the ground.

Right at the ground, there is no wind, thanks to the drag of the ground. And up at a large altitude, you'll have the full effect of the wind, but as you get lower, the wind speed will decrease.

This gradient causes at least two problems close to the ground --

1) when you're landing upwind, you lose airspeed as you descend. This is generally a good thing, as it helps `suck' the plane into the ground and prevent balooning, but it does mean you don't want to come down for a landing right at your stall speed.

But when landing downwind, you gain airspeed as you descend, which causes balooning, and the effect is very pronounced.

2) if you're doing a steep turn at low altitude, the lower wing will be in air with a lower wind speed than the upper wing, due to this gradient. The effect is especially high with gliders with long wings.

In any event, if you're flying upwind at a low altitude and enter a tight bank, the airspeed over the high wing will be higher than that over the lower wing, which generally means that it'll create more lift. This will tend to pull the plane into an even tighter bank and has probably caused the death of more than one full scale glider pilot (since they're low and don't have enough altitude to recover from a nearly 90 degree bank.)

Actually, I may have answered my own question about `why you'd have to turn tigher downwind' -- going downwind, the airflow over the lower wing would be higher than that over the higher wing, which would tend to pull your plane out of the bank, requiring more pressure on the stick. Of course, this would only be a signifigant factor close to the ground and especially with a plane with a large wingspan.

Of course, this is all about steady winds -- if you have gusts of wind, or lulls in the wind, they'll certainly affect your airspeed.

| Tim Wescott wrote: | > Roll control on both the full scale craft and on that model is via | > spoilers on the wing tips, which lose effectiveness at low airspeeds. | > Couple that with the anhedral, and if you let it get to slow and rolled | > too much it'll go over on it's back. | | Right, and in addition, the B52 doesn't have sufficient rudder authority | to keep the nose up in extremis.

Of course, that's true for most non-aerobatic planes.

There's a reason that the full scale plane instruction manuals are very specific about things you should not do -- like do not bank over

30 degrees, ever, or don't let your speed drop below X mph ... when these things aren't followed, people die.

Unfortunately, when you build a model from scratch, you don't get the benefit of such an instruction kit and the testing that went into it, unless you go searching for the flight manual for the original plane, and even then many of the warnings may not apply.

Though if you ask me, I get upset when I destroy an ARF that I put 20 hours into assembling. 2000 hours? I'd be afraid to put the plane in the car, let alone actually take it airborne ...

To maintain your ground track. We (I say we in including anyone else who flies "full scale") practice maneuvers all the time during initial pilot training to maintain ground track. Not a week ago I was doing high-recon in a helicopter and really had to turn hard from the downwind leg to keep from being blown away from the pinnacle I was about to land on. Turning from the upwind I had to finesse the helicopter around the turn to keep from being blown towards the pinnacle.

Same thing happens in a traffic pattern.

Not entirely true. Near the ground, friction reduces Coriolis Effect, it doesn't eliminate wind altogether. Sure, the surface may slow it down a bit, but it can also increase it. (Look up Katabatic Winds) You should try changing the oil on my truck in my driveway. There's ALWAYS a good breeze blowing as I live at the bottom of a valley. Unless I put up some sort of wind barrier, the oil goes everywhere but the drain pan.

Actually, you lose groundspeed. Airspeed is the speed the aircraft "feels" as it moves through the relative wind. If I have a 20 knot headwind right off the nose and I'm indicating 70 knots, my groundspeed will be about 50 knots. The airplane "knows" it's flying at 70 knots and doesn't care it's only covering 50 nautical miles in an hour.

This is exactly why runways are built to "face" the prevailing winds and why aircraft carriers turn into the wind and pour on the coals, to increase lift. As for landing, you DO want the aircraft to stall just as it touches down.

Nope. You actually lose airspeed and gain groundspeed. Again, 20 knot tailwind, indicating 70 knots my ground speed will be around 90 knots. Ask a pilot friend with a GPS to take you up and check the groundspeed on the GPS against the airpseed indicator. How many aircraft have impacted the ground short of the runway when they encounter a headwind to tailwind sheer??

I asked a student pilot a couple months ago, "Can you fly a helicotper backwards at 25 knots on a calm day?" He answered, "No." I then asked if he could hover a helicopter with a 25 knot tailwind. he said "Sure." I then asked him, "What's the difference?" He didn't understand the relative wind across the rotor disc and along the aircraft would be 25 knots from the rear in either case and the aircraft would only know it was flying "backwards" at 25 knots.

Has nothing to do with the wind. Once you're aloft, the aircraft moves along with the airmass and unless it's really gusty, the airplane doesn't care what the wind is doing. All it knows it that it's flying at some airspeed and attitude.

The death spiral you describe is a pitch problem, not a bank problem. Altimeter is winding down, plane is banked hard over and the pilot hauls back on the yoke in an attempt to stop the descent rate. This only tightens the turn even further..

True, but again, once aloft, the aircraft doesn't "feel" the wind. It only moves along with the airmass it's flying in.

Yet rudder in opposite the falling wing is the recovery technique for stalls. There's got to be enough rudder authority to get that low wing moving forward through the air, increasing it's relative wind and therefor lift, to get it back up. If you add aileron to correct the dropping wing, there's a very good chance you're going to enter a spin

- where you'll use rudder to stop the spin and recover.

Bank angles have to do with G loads, nothing more. (Unless you can't fly coordinated but I won't get into skids and slips) The more you bank, the higher the G-loading. 60 degrees of bank equals 2 Gs. Most GA aircraft are rated to 3.8 positive Gs (The Normal category or is it Utility?. I keep forgetting which) which would be around 75 degrees of bank. Most GA aircfraft don't have the power to maintain that bank angle in any case. Anytime you bank or pitch an aircraft more than 30 degrees, you're required to wear a parachute by regulation.

As for the speeds, the Operator's Handbook will list things like Stall speed for both clean and dirty configurations, minimum controllable airspeed, maneuvering speed, etc.. Each is a performance limitation based on what a test pilot can do with a brand new aircraft on a "perfect" day. I've flown below stall speed in Cessnas and Pipers a hundred times and I'm still here. Stalls are part of a pilot's training almost from day one. Stall down low and yeah, you're probably gonna ball up the airplane.

As you know there are 3 kinds of radio controlled aircraft:

1) Those that haven't crashed. 2) Those that are going to crash 3) Those that will crash again.

It's part of the hobby.