M4 Handling

[Flyjohnny]

Hey Maule family,

I bought a 1968 M4 in May of this year and have spent the summer trying to fall in love with it. Just a quick note about my background, I have over 18,000hrs and have flown airliners and bush planes for years. I had a Stinson 108 for the last 3 years with a 180hp engine but have always loved Maules so jumped at the opportunity to get a M4 210C. I really have enjoyed the performance of the plane in almost all environments except one. I loaded the plane up with full fuel, my wife and I in the front, sister along with 90lbs of dogs in the back seat then about 80 pounds of gear in the cargo area. Once we were up in cruise, over the Georgia Straight in BC, I noticed that the plane was very, very pitch sensitive and almost unstable. Even with slight turbulence the plane would cause the plane to almost start porpoising. To me it really felt like a plane that was way out of C of G to the rear of the plane. The pitch sensitivity made it quite tricky on approach and landing at slower speeds as well. Once on the ground I rechecked my weight and balance numbers expecting to find something out of wack but the numbers were right on center. When I fly the plane with two people up front and keep all the cargo weight up as close to the back of the front seats the planes is an absolute dream to fly. My concern is that I really want to have a true 4 seater airplane but am hesitant to load up 4 adults and a small amount of gear in the cargo.

As far as mods on the plane it has VG's and elevator gap seals. The trim indication never seems to be far off the neutral postilion during cruise or approach as well. I have thourolly looked through entire plane looking for something odd but haven't found anything unusual. Also removed flooring and panels to verify that there is no weight added in the tail or anywhere else.

What I am trying to find out is if these are normal characteristics for the M4? I know that it is generally know to be a bit more tail heavy compared to the M6 and later models but again looking at my C of G everything looks normal. I am really looking for some input from long time M4 owners who could point me in the right direction to make the plane fly more stable. Any ideas fixes that anyone has found helped make a big difference like moving the battery forward ect. Also if there is anyone who has a significant amount of time on the M4 as well as other models like the M6 I would love to hear there experience. Please let me know if there is something I can do or if this is just normal for the M4

In the end I want to fall in love with the M4 and invest some of time and money fixing it up so it could be my long term plane but I also want a true 4 seater and need to be comfortable with its handling capabilities.

Thanks for your time gang.

[Kirk]

M5 driver here not M4, but pretty similar characteristics. Never heard of such a dramatic difference at a more aft cg as you describe. Something’s not right.

I would check the integrity of the control cable routing for both elevator and elevator trim, cable tensions and elevator hinges. Also, lightly clamp the elevators in neutral with the horizontal stab and check the elevators for warping. See if the resistance in the controls fore and aft feels solid while it is clamped.

Wondering also how recent or valid the W&B is. Could be heavier and more aft than what’s on paper.

Kirk

[yanknbank]

In my m5 210c, 350lbs in the front seats, 230lb in the back seat and 80lb in the baggage with full fuel is outside the aft cg range.

[firstmaule4]

My m4 220 would be out of balance as well I do not have the numbers in front of me right now but no way I could add fuel fuel and all that weight and be in envelope Pretty sure I would be over gross as well with 62 gallons of a gas and 4 people and cargo

[Flyjohnny]

I appreciate your responses and wanted to give you a some more accurate number for the C of G for that day to show that I was in balance according to the manuals.


Weight Arm Moment

Aircraft empty 1317 11.1 14619
Front Passenger 320 20.0 5800
Rear Passenger 230 53.0 12200
Baggage 80 72.5 5800
Fuel 240 24.0 5800

Total 2187 44819 Divided by 2187 = C of G 20.49

Not right in the center as I stated but definitely within limits and yes, the weights are accurate. I have attached the weight and balance forms as well. I realize that the C of G would have been more reward but still the plane shouldn't have been this unstable feeling. Really appreciate your input.

[vaughans]

Have you weighed your plane? Seems light unless really stripped, Both of my m-4 220's weighed in at around 1450 empty weight. Would not consider the m-4 to be a true 4 person & baggage aircraft & would want to verify empty weight if loading toward full gross.
Vaughans

[Kirk]

Have you weighed your plane? Seems light unless really stripped, Both of my m-4 220's weighed in at around 1450 empty weight. Would not consider the m-4 to be a true 4 person & baggage aircraft & would want to verify empty weight if loading toward full gross.
Vaughans

Was thinking the same. Really haven’t seen any that light. Which means the documented cg would be pretty suspect also.

I would still be concerned about control cable integrity and tensions.

Kirk

[Andy Young]

I also find the empty aircraft numbers suspicious. You show an empty CG of 11.1. Apples and oranges to some degree, but my M-6-235 has an empty CG of 10.7 (very close to your 11.1) but I have a 400 lb. IO-540 hanging off the front. Hard to believe a 210 would have a CG that far forward, but I’ve never owned one, so I don’t really know. Running your loading numbers on my M-6 gets me a gross weight of 2466 lbs., (34 pounds under max gross) with a CG of 18.04”, well within range (aft limit is 20.5”). That’s a big, but manageable load for the M-6-235; seems a bit large for an M-4-210.

Anyway, your symptoms do sound a lot like an aft-of-limit CG. Might be worth weighing your plane, or looking for an error in someone’s recalculation of empty weight and CG from maintenance work in the past. Wouldn’t be first time I’ve seen that.

[yanknbank]

My io360 m5 is 13.2 empty cg. Is the m4 that much lighter in the tail? 1330lb empty on paper, but I'm sure it's heavier. Your empty weight doesn't seem that unbelievable though. The early maules were much lighter

[yanknbank]

This is my cg for your conditions. It's barely out. I've flown there and never had issues with instability. I see your envelope is a bit wider too. I'm at a loss unless your numbers are wrong.

[Flyjohnny]

Here is a copy of the last C of G calculation that I am aware of, like I said the plane has only be mine for the last 4 months. This is last weight and balance that I have and it shows it was done in 2009. The plane is pretty light in the avionics department. Really just has turn and bank, VS, Altimeter and Airspeed plus single radio and transponder. No vacuum system. I would be interested to see other peoples scale numbers.


Thanks

[vaughans]

Just sayin, I had both on the scales. 1st was a 73 m-4220 std tanks, razorback, ifr #1450, 2nd 68 m-4220 with aux tanks, ceconite, VFR #1445. both had 8.50s & scott tail wheel. I would weigh yours on a set of certified scales. Bet you'll be surprised.

vaughans

[Dkuber]

Your load in mine.
Heavy, yes. Doable, yes. Mine would not be unstable at that load. M4-220

[Flyjohnny]

Your load in mine.
Heavy, yes. Doable, yes. Mine would not be unstable at that load. M4-220

What is your empty weight and C of G for comparison. My plane is pretty stripped down, not headliner and just a couple of side panels. I imagine that your Franklin will be a bit heavier than min IO-360 bringing the weight forward a bit. I also have very little avionics.

[Flyjohnny]

Has anyone out there actually moved the battery forward in an M4? I have seen a couple of people talking about it and one person who said his battery had been moved under the front seats before he bought the plane. Just wondering if anyone has done it and what differences they noticed.