m5-235 cruise speed

txmaule · Post by **txmaule** » Mon Jul 07, 2008 6:37 pm

I have 8.50's, and the usual antennas
I’ll have to check the rigging cuz it sounds to me that mine is slower than it should be. the 118 knots was in high humidity and about 90 degrees.

Can the type/length of prop change anything?

skip k

TomD · Post by **TomD** » Mon Jul 07, 2008 7:36 pm

I have a M5-235C w/ O540-J1A5d, micro Vg's, 8.50 tires ( not tyres Jeremy), three blade McCauley, and common aerial array. I putt along about 118kt 20" mpi, 2100-2150 rpm at the 6500' range and leaned to about 50 degrees rich of peak.

I burn about 12 gph at that setting. I find the increased speed at 23" and 2300 rpm just ain't worth the fuel burn.

TD

maules.com · Post by **maules.com** » Mon Jul 07, 2008 7:46 pm

Just for info my present M7-260 returned 11.5 gph in 17.5 hours of the JC flyin trip. Flying from 500msl to 11200msl at various power settings. Lowest gph for any length of time being 9gph with IAS of 118mph.
Fuel burn is directly related to hp used. 180, 235, 260 all return similar fuel burn specifics. I was on the ABW 26" with vg's and full IFR antennas.

210TC · Post by **210TC** » Sat Jul 12, 2008 7:45 am

I almost forgot?
Some of the Maule airframe were not rigged properly during the welding process. This caused wing attachment fittings on the fuselage to be off.
On my plane it is about one degree. Now, the factory's jig is fixed and this no longer happens.
When I first purchased Betsy she was placed in a hanger for super check up. During this process we leveled and re-leveled trying to get the wings perfect. We found the attach lugs to be off. We split the difference and that is all that can be done without a major operation.
If your plane is slow or has a pulling problem find a good level slab and get out the books. If you need to change or adjust the struts remember this. Attach the longest strut first requiring you to PULL the wing DOWN to install the bolt on the second strut. This is far easier than holding or pushing up the wing to install a bolt. I was told the opposite by some real Maule experts and the push up method is a super duper bad idea.
You can spend several days tuning your bird and adjusting things if you like perfect and perfect + Maule is a littlle out in left field. I suppose this is why jeep never qualified at Daytona

a64pilot · Post by **a64pilot** » Sat Jul 12, 2008 8:37 am

Just don't take the wash out, out in the search for speed. If you do, you will change the way it handles in a stall.

SkyMaule · Post by **SkyMaule** » Sat Jul 12, 2008 9:21 am

I have a 1975 Maule M5210C. I have had it six months. We have put 100 hours on it. Normal Cruise is 7-8 thousand feet. I figure 116 knots for cruise. That is firewalled and 2400rpm leaned to peak. Fuel burn is 9gph.

210TC · Post by **210TC** » Sat Jul 12, 2008 12:24 pm

SkyMaule,
If you are indicating (not true) what you stated at 9gph, I think you are doing well. I think you are about or close to one gallon better than I. Some have told me that the Turbo charged Lycoming burns a bit more per HP than a non-turbo.
When I get her back into the air with the new Fuel Flow Gauge I will be able to find the exact truth. All of my past records are from fill up to fill up.
With today's fuel prices I think we will all learn more about cutting fuel cost.
Who knows, we could even see some speed mods in the future

maules.com · Post by **maules.com** » Sat Jul 12, 2008 1:10 pm

Lycoming books show that most efficient fuel burn for distance is 55%+ in a headwind and 55%- in a tailwind, while best fuel efficiency for time spent in the air is 45% slightly dependant on cg loading position.
Take into account High MP/ Low RPM = Low GPH/ Higher Temp.
Low MP /High RPM = Lower Temp/Higher GPH
MP rises 1" per 250 RPM decrease which produces better volumetric efficiency.

SkyMaule · Post by **SkyMaule** » Sat Jul 12, 2008 3:14 pm

210TC wrote:SkyMaule,
If you are indicating (not true) what you stated at 9gph, I think you are doing well. I think you are about or close to one gallon better than I. Some have told me that the Turbo charged Lycoming burns a bit more per HP than a non-turbo.
When I get her back into the air with the new Fuel Flow Gauge I will be able to find the exact truth. All of my past records are from fill up to fill up.
With today's fuel prices I think we will all learn more about cutting fuel cost.
Who knows, we could even see some speed mods in the future

David,
I am really intrigued by your turbo 210. I have flown seneca's and a skymaster with the TIO-360's. I've thought they perform quite well. That must make quite a machine out of the M5!

The 116kts is true. When winds are behind me I will go to ten or eleven thousand. Fuel burn goes down to 8 gph. I'm guessing true at around 108kts at these higher altitudes. We came back from Smiley Creek to Bismarck on 39 Gallons of gas in five hours. 11,500ft 650kt+/-

Mark

210TC · Post by **210TC** » Sat Jul 12, 2008 4:41 pm

I found one more picture. If you figure this out I am at 118 Kts indicated @ 17000 ft = 158 Kts true = VNE
Another reason to stay away from TAS

calm down Betsy

SkyMaule · Post by **SkyMaule** » Sun Jul 13, 2008 5:34 pm

SkyMaule wrote:
210TC wrote:SkyMaule,
If you are indicating (not true) what you stated at 9gph, I think you are doing well. I think you are about or close to one gallon better than I. Some have told me that the Turbo charged Lycoming burns a bit more per HP than a non-turbo.
When I get her back into the air with the new Fuel Flow Gauge I will be able to find the exact truth. All of my past records are from fill up to fill up.
With today's fuel prices I think we will all learn more about cutting fuel cost.
Who knows, we could even see some speed mods in the future
David,
I am really intrigued by your turbo 210. I have flown seneca's and a skymaster with the TIO-360's. I've thought they perform quite well. That must make quite a machine out of the M5!

The 116kts is true. When winds are behind me I will go to ten or eleven thousand. Fuel burn goes down to 8 gph. I'm guessing true at around 108kts at these higher altitudes. We came back from Smiley Creek to Bismarck on 39 Gallons of gas in five hours. 11,500ft 650kt+/-

Mark

David,
I wasn't paying attention...........I was thinking a 210TC would be a turbo'd version of my continental io360. I thought pearl and betsy were cousins! Theyre not even related. Pearl lives a block further away from the gas station

210TC · Post by **210TC** » Mon Jul 14, 2008 10:05 pm

The issue about VNE was brought up. Is VNE calculated from True or Indcated air speed? Most all GA aircraft use indicated because they vary rarely see high altitude and when they do they have no power to reach a concerned high speed (vne). Aircraft capable of high altitude flight are to be equipped with airspeed indicators that indicate TAS if they are capable of reaching VNE in TAS #'s.
TAS is the true speed of the aircraft traveling through the air and the effects of that air on the airframe/flight controls remains the same. If I firewall at 17000 I can exceed the design limitations of my aircraft based on true airspeed which is the same as IAS at low altitude. This is all based on the air traveling across the airframe. I will try and find the reg on this issue, it could be 23.450??
I found this and the author is much better at it than I. Vne is 'Velocity Never-Exceed'. It is the fastest you can go without breaking stuff, as indicated on the airspeed indictor. Let's say that Vne for your airplane is 200 knots. That means that at sea-level, you better stay below 200 knots or the air pressure can pull the plane apart. Now, let's say you go to 20,000 feet and (with a turbocharger, pushing the nose down, or just having a huge engine) you manage to get the airplane up to 200 knots indicated airspeed. The airplane is ACTUALLY going about 275 knots. This is because the air is thinner, so it does not push against the wings as hard, and it does not push against the pitot-tube as hard. Because the air is thinner, you are really going 275 knots, even though you are only seeing 200 knots on the airspeed indicator due to the thinner air and resultant lower pressure on the airplane. Now, most pilots will read the sentence above, already know what I just said, and think that they must be OK going 200 knots indicated at 20,000 feet, since they are still below Vne. Possibly WRONG!!! The airplane may be over it's maximum FLUTTER SPEED. The FLUTTER speed is the speed above which the structure of the airplane will oscillate and then disintegrate. The flutter speed is NOT an INDICATED airspeed. It is a TRUE airspeed. In other words, if the flutter speed of the airplane is 200 knots at sea level, then it is 200 knots at 20,000 feet as well... which is only 145 knots ON THE AIRSPEED INDICATOR! In other words, your REAL Vne will come DOWN from 200 knots at sea level to 145 knots indictaed at 20,000 feet IF the speed-limit on the airframe is dictated by FLUTTER (which is a constant TRUE airspeed) vs pressure loads (which are a constant INDICATED airspeed). In other words, if your airplane has it's Vne determined by flutter, not pressure loads, then you need to never exceed that TRUE airspeed, which means that you need to go to a LOWER INDICATED airspeed as you climb to keep from exceeding that TRUE airspeed. So, at high altitudes, be ware! Just because the air is thinner does not always mean that you can push higher speeds... the FLUTTER speed does not increase as you climb, yet your TRUE speed does... at some point, if those speeds converge, then your next convergence will be with the Earth... in whatever pieces are left of your airplane!

Now, a good question is: WHY is it that flutter is a TRUE airspeed? Well, Vne is based on INDICATED airspeed since INDICATED airspeed is an indicator of PRESSURE, which is what is pushing back on the wing. But FLUTTER is a different deal. Let's say a bit of air pushes the elevator UP. First things first: YOU THINK that the elevator rotates about it's hing-line. In the case of flutter, you are SOOOOOOOOOOOOO wrong. The elevator, like ALL objects, initially tries to rotate ABOUT IT'S OWN CENTER OF GRAVITY!!! This may be halfway between the hinge-line and the trailing edge of the elevator! The hinge of the horizontal stab just tries to prevent that from happening by exerting a vertical force to prevent the elevator from rotating about it's center of gravity, and forcibly rotate the elevator about it's hing-line instead. But, when flutter happens, the aircraft structure becomes elastic compared to the forces at play. In the flutter case, let's say a bit of air pushes the trailing edge of the elevator UP... since the elevator tries to rotate about it's own center of gravity, this pushes the leading edge of the elevator DOWN. This actually pushes the trailing egde of the horizontal stabilizer DOWN! The horizontal stabilizer then SPRINGS BACK to where it was before, which shoots the LEADING EDGE of the elevator UP. Since the elevator rotates about it's own center of gravity in an elastic aircraft structure, the LEADING edge of the elevator going UP causes the trailing edge of the elevator to go way DOWN. OOPS! We just found the elevator went down possibly FARTHER than it was deflected UP! This is the definition of a divergent oscillation: A larger deflection, in the opposite direction, each time it oscillates about the center-point. It continues until the structure breaks. TRUE airspeed is what drives when this can happen, since the whole idea is that the resonant frequency of the springiness of the airframe must be in harmony with how fast the elevator wants to flap around in the airstream... and this will happen at some TRUE speed of air moving over the surface, since that, in fact, is what will determine how fast the elevator moves. (a motion wich better not be in resonance with the natural oscillating frequency of your horizontal stabilizer!) Now, I will concede that some INDICATED airspeed is ALSO needed to wreck your plane, since you gotta have some FORCE to make the thing gyrate out of control, but the flutter speed is TRUE, not indicated.

MYTH: AT POSITIVE ANG

a64pilot · Post by **a64pilot** » Tue Jul 15, 2008 5:46 am

David,
I think a little knowledge is a dangerous thing. Our Aeronautical engineer is gone this week getting training in solid works ( a cad / cam program) or I would step over there and ask him. I think that true airspeed comes into play when VNE is determined by compressibility because I think the speed of sound would be a true airspeed constant. I don't think a Maule will ever have to worry about compressibility

Usually on small airplanes flutter is not the limiting factor for VNE.
OK, I went and asked the other aeronautical engineer we have. Nice kid, but he is straight out of school and there are no simple answers from him. As far as I could get from him, compressibility and flutter are functions of true airspeed, but if your VNE is determined by aircraft structure, say like maybe the windshield by a wide enough margin so that it would basically be impossible to achieve a true airspeed that could get you into flutter prior to reaching the indicated airspeed limit of the windshield, then the indicated airspeed can safely be used as the VNE.
I don't know because I don't fly them, but I would expect fast aircraft like biz jets maybe would have a VNE that is a Mach # because of compressibility being their limiting factor.
I think as long as you stay within whatever limits your aircraft was certified at, there is plenty of cushion for safety.
I know your turbo is fast, but I don't think you can hurt it in level flight. I wouldn't worry about it.
On edit, flutter is such a scarey thing, I believe it's common practice to weight your control surfaces to the point to where flutter just isn't a possibility. The only flight test fatality that I know of where I work was in an Aero Commander 112 during flight tests for flutter. It got into flutter, the tail came off, the pilot escaped and the flight test engineer didn't.

210TC · Post by **210TC** » Tue Jul 15, 2008 6:52 am

A64,
I was pm'ed about this issue, so I thought I would post some facts.
I am not here to second guess why Maule placed a red line on my indicator.
Even if I had knowledge that the factory test indicated no flutter I would not exceed VNE at TAS. This is an area that I stay away from for three reasons.
1. regulation 2. I have witnessed flutter and it was a frighting event. 3. Flutter can happen at unconceivable slow speeds.
The piece I attached was not written by me.

SkyMaule · Post by **SkyMaule** » Tue Jul 15, 2008 9:06 am

Yesterday I was at 40,000 feet in a Citation 560. The indicated was 230 the true was 430. Vne below 8000 is 262 . (bird strikes on windshield) above 8000 feet it is 290. somewhere around 28500 it changes to vmo .75

Vne is indicated. No need to worry about true. True is for bragging about!

m5-235 cruise speed

Speed

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