m5-235 cruise speed

[210TC]

You guys are bringing in Indy Cars when we are taking about Jeeps.
The intent was to clarify VNE as to the faa requirements and the reasons behind these rules.
My posting about Betsy at VNE indicating 118 kts caused someone to write me an email. I have owned a couple of the fastest GA aircraft around (not Betsy) and this is an issue that is worthy of conversation.
Lets keep this away from mach #'s.
And yes I like to boast about Betsy when she gets "high". She is the most amazing plane I have ever owned. She can get rough, down and dirty and fly with the eagles at speeds one would expect from a very expensive airplane.
I out ran a v-tail bonanza from southern CA to Nevada once due to her ability to get to altitude quickly and make power.
You will also note I regularly refer to "IAS" do to the many variables. However, with my training at high altitudes I always convert to "TAS" unless I have contradicting valid information.

[a64pilot]

I'm not picking on you or Betsy, but as long as you keep her within certified limits, including the indicated VNE you'll be OK. No need to worry about what your true airspeed is as far as VNE or there would be a placard or warning in the book etc. Flutter scares me too. I've never seen it on a full size airplane, but I know that I don't want to.
Talking about throughbreds though, you know what determines the service ceiling of a U-2?

[210TC]

I disagree on I should not worry about true air speed. I think you are correct about the placard, yet none exists. Who would of thought of a Maule at the altitudes Betsy goes to. You would not believe all the conversations I have with the feds "What kind of Maule are you?' " Your are a what/" "please repeat?". Given this, I think 10 Maules slipped through the cracks "fed regs"
I need to find the reg's and post them.
Yes, please tell us about the U2.

[SkyMaule]

David,
What do you find to be the best cruise altitude for Betsy? We had a turbo 210 at work. It seemed that 10 to 12 thousand was where it performed best.

My point in bringing the Citation into the picture was that even at 28,000 in the decent you can run er right up to 290 indicated while true is well over 400. It also validates your observation that indicated is not always the limiting factor since for us at 40,000 ft. mach.75 is reached at somewhere around 235 IAS depending on temp, press, etc. and at lower altitudes the limit is 290 indicated. You know much more than I do about flutter etc. I just know that in production aircraft Vne is IAS. As a64 says: if there were other limits it would be placarded somewhere. Perhaps the service ceiling may have something to do with that also? I don't know. Ive already said more than I know about this.

Ive always said its not the pilots that are amazing. It is the engineers. Im glad they figure all of this stuff out and make these wonderful flying machines like Betsy and Pearl for us!

Peace

Mark

[a64pilot]

Off of the top of my head I want to think we are both certified to FL 180. I haven't looked at the TCDS. I assume you could, but why would you want to go much higher than FL 180? You have to be on an IFR flight plan and I assume fly the high routes. I would think other things like OAT and turbo life would be more of a factor above FL 180 than true airspeed.

[a64pilot]

Nope,
I just looked it up the 210TC is certified to FL200 unless I somehow looked at it wrong.

[210TC]

The only reason to go above 18,000 is weather. And once on an IFR flight I went to 23,000 in an attempt to get above the Ice. The situation warranted exceeding FL20. Fl20 is the certificated max altitude, only because no one attempted to show she could go higher and the instruments being certified to this altitude.
Fly from Watson Lake to White Horse (Canada/Yukon) direct and you will want to be at FL40. It scared me at 17,000. The air conditioning works great up high and she rides like a Cadillac. The flight to White Horse was an exception, I froze.
I don't know the best cruse altitude. Just to many variables, with the new fuel flow gauge I will be able to obtain some real good info later when back in the air.

[Duane]

Off subject. but Wow.. a maule at 23k? no wonder the controlers drink. lol

[MikeW]

Ok, I'll bite.

The VNE indicated is the limiting factor of your airplane unless otherwise stated. On an airplane like the Maule, VNE will be exceeded before other aerodynamic limitations are reached ie compressibility, flutter etc... Jets are concerned with compressibility and the shockwaves that go along with that. Turbo-props and high performance piston airplanes will have high speed limits that are unique to each aircraft design and these limitations have to be established prior to certification. It could be flutter, or compressibility. Some of the WWII airplanes were runnning into this in high speed dives. This information is usually provided to the pilot via a movable red line or barber pole on the airspeed indicator. The higher you climb the red line starts to move down on your airspeed indicator. On the aircraft that I have flown this "transition" occurs right around 25,000 ft. Take an airplane like the Twin Otter, it only has a VNE speed, about 160kts indicated. You can take that airplane to FL250, tip it over and descend at the barber pole, which is still 160kts and the airplane is within limits, even though the TAS would be well over 200kts. The VNE speed of a 737 is 340kts indicated, but as the airplane climbs the barber pole drops until at FL 370 the max indicated speed is about 242kts. To suggest that an airplane, like the Maule, that is being operated within airspeed limits will come apart because the pilot didn't figure his TAS that day, is misleading.


Mike

[210TC]

Ok Mike,
For Pete's sake let go to 17,000 ft and speed up to VNE (indicated) which is 158 kts. This is 212 kts true or 243 MPH. Would you fly with me without a parachute in my Maule?

[MikeW]

Well, that depends. Do I get a O2 bottle? As far as the airplane goes, it would do just fine.



Mike

[aero101]

Vne is based off indicated airspeed and has nothing to do with TAS... That is the advantage of having a turbo'd airplane is that you can climb up into the FL's, still make reasonable power which will translate into reasonable indicated airspeeds, and will true out quite fast!!! The structural load on the airplane at 158kts indicated airspeed is the same at 1,000' as it is at 20,000'... IE, the air is much more dense down low, more drag, therefore TAS much lower.... Up high, air thinner, less drag, therefore TAS much higher, the airplane doesn't know the difference up high - down low, it's all the same total drag at given IAS... With jets, turbines, etc above FL25, and higher airspeeds, it's another ballgame and really not at all applicable to us little guys. As for the warbirds in dives, they are exceeding their VNE's or in the case of their test program when they were new, they are establishing VNE's...

[210TC]

I am surprised here.
It is Flutter that I have been trying to point to.
Set aside density altitude for a moment.
"Air Speed" is unaffected by density altitude. At 1000 feet 158 kts indicated is air traveling over the control surfaces at 158 kts.
At 17,000 158kts indicated the air is traveling across the control surfaces at 212 kts.
The size of the molecule does not effect the speed in which the air travels accross the control surface.
I understand the point that several of you are trying to persuade me with.
I am a thinker, but I don't have a degree in physics. Any of you blessed with such a degree? If so, please shed some light on this subject.

[yellowbelly]

210TC:

Flutter IS scary partly because so many variables are involved. You have to account for the interaction of the "springiness" or stiffness of the structure, the aerodynamic loads, the mass distribution of the components involved and any damping forces, aerodynamic or otherwise acting in the system. At the design phase, all of these are modeled as damped spring-mass systems, a simplification to help quantify all of the above. By manipulating stiffness and mass distribution, you can tune the system to move flutter out of the picture to a safe speed. The scary part in my opinion is how sensitive the picture may be to small changes in any of the variables. That's why you have to weigh and rebalance control system components after painting or minor modification. Some flutter accidents followed control surface removal and replacement with the mass balance weights omitted.

Your TC'd Maule is a jewel. You are correct that the TAS over the elevators is higher up there, and a molecule still weighs the same up there, but there are a lot fewer of them. The aerodynamic forces on the elevators, etc are reflected by what's showing as IAS. What's NOT being reflected anywhere is any aerodynamic damping which is probably reduced considerably at high altitudes. Without damping, your flutter margin will be reduced. If you are changing any other parts of the equations, maybe by having improperly balanced controls or worn hinge pins which might allow a buzz to start, there will be less damping force to stop it or limit it. If real flutter does start, the show will be over before you can utter a four letter word.

I wouldn't be that concerned about your TAS up high. Wish I could match it in fact. As long as you keep everything tight and well maintained, I'd bet you have plenty of margin from the flutter speed. It might be tempting to look at that simple Maule empennage and want to thicken it up to make it stronger, stiffer and more able to resist flutter, but because so many other aeroelastic factors are involved, it is quite possible to drop yourself right into a danger zone because everything else changes when you alter one item. TAS is not necessarily the driver in flutter incidents. Ever seen that tape of the Tacoma Narrows Bridge failure? That's a classic study in aeroelasticity and flutter in slow motion.

YB

[210TC]

I have seen the tape of that bridge near Tacoma.
Back in the early 80's you may recall an aircraft built and designed by Mark Brown that won Oshkosh. It was called the Starlite and was on the front page of EAA's magazine. Mark contacted me to fix a problem with his induction system and make sure the engine was up to snuff for Oshkosh.
Another man and myself stood next to the runway as Mark was approaching
in a decent for a fly buy about 1/4 of a mile away. The aircraft turned into a dot with the most chilling sound I had ever heard. I knew Mark was dead. Mark reduced power, pulled the nose up and landed the plane. Mark said the vibration was so severe he could not see, he to thought he was dead. Mark said something to the effect that it was impossible the plane was intact and it should have disintegrated. Not even a crack was found anywhere on the airframe (composite). The problem was flaperons. Mark asked us to keep it to ourselves until after Oshkosh and then he would install normal flaps and announce or make public what had happened. Mark is one of a few engineer's in the world to receive some special awards for his contribution to aviation.
This story will let you understand my fear of flutter. I have read conflicting stories similar to post on this thread, BUT I will stick to my guns until someone tests the Maule to speeds that we have spoken about