Deathtrap MU-2 BANNED

[avbug]

I hate to disappoint you, swass. Actually, that's not entirely true, but I'm going to disappoint you, and deal with the self-loathing, anyway. No sparks of brightness for you, today.

Agreed that you can use that to very good purposes, like landing in a very, very short distance, or descend in ways that ATC can't believe. And,,, if properly adjusted, they should not pulse. But most are never adjusted that well.

The Garrett may be set up in many ways, and all may be proper. The design of the airplane, and the maintenance documents attached to it, enable it be set up not only for a particular installation, but for a particular operator.

Ours were set up such that bringing the power levers to idle nearly tossed you out of your seat; the airplane could be pointed practically straight down and nearly stall out...that much braking action. When I first got in the airplane I had been in the same type with a PT6 engine on it, and out of habit pulled the power lever to idle during the landing. The airplane fell out of the air. During an hour and a half introduction to the airplane, I did a record number of go-arounds as I tried to find the sweet spot on that power lever.

In that condition, which is properly set up for that application, in a very steep dive down a canyon or hillside, the airplane will be felt very strongly to pulse as the NTS pushes the blade angle toward coarse. The flip side of it was found when I flew an airplane that hadn't been rigged quite right. The fuel control and the underspeed governor were discovered to fight each other if the speed control backed off the forward stop at 100%. We had to readjust the speed control bottom end (underspeed gov) to 98% instead of 96% because it was fighting the fuel control and causing massive engine surges. This wasn't learned until a throttle quadrant developed some play and the speed control backed off in flight. Power rolled right back to idle then surged up again, and kept doing it in increasing cycles.

It was a definite attention-getter.

 

[Berkut]

Well, no, half are below the median. It doesn't necessarily follow that half are below average.

Hence the "probably"

 

[Say Again Over]

Nts

I agree with the previous post that flight idle fuel flows can be set up to Pulse or not to Pulse, it's really an operator preference. As far as whether the system is working properly, it's very easy to check during start up, if you don't verify that it's working, you get what you get, I've turned engines off at a safe altitude without the system working properly and there is tremendous yaw, not something you'd ever want to see just after takeoff.

 

[Bringupthebird]

The Cessna 208 Caravan deserves far more scrutiny than any MU-2. Mr. Tancredo should look at the abyssmal accident rate of that thing first. IMHO, no single engine should be allowed in commercial service at night, IMC or in icing.

 

[GoingHot]

no single engine should be allowed in commercial service at night, IMC or in icing.

That would take out a lot of airplanes currently flying everyday in those environments. The 208s alone, number several hundred.

CE-208
CE-210
CE-207
PA-32
PA-46
TBM-700
PC-12
others

 

[avbug]

I agree with the previous post that flight idle fuel flows can be set up to Pulse or not to Pulse, it's really an operator preference.

The pulsing on descent is actually the Negative Torque Sensing (NTS) system, which isn't a fuel adjustment. It's the governor driving the prop to coarse to apply positive torque, or a load, to the driveshaft.

The fluctuations that take place due to the speed adjustment interference occurs when the bottom end of the low speed governor is set close enough that when the power is pushed up (and the speed lever set back to lower RPM), the prop governor tells the fuel control to pull the power back, and then causes a reduction in fuel flow. The fuel control senses this as going underspeed and applies extra fuel, and the surge is interpreted by the governor as an overspeed and it takes away even more fuel. The engine begins to surge. The simple soloution is to set the bottom end of the propeller governing range up a little.

Personally I think it's a poor design that's capable of getting to that point as a function of normal positioning of the engine controls...but it is possible, even within a properly adjusted engine set according to the manufacturer.

 

[Hung Start]

Once again, I understand about the fuel flows and the pulsing. I know it can be set up either way, and having flown at least one that was not set up well,,, oh yeah, it grabs your attention. Especially if one is a "hard" low pitch and the other is not. Talk about yaw!
But (and I am the first to defer to Avbug on this, because I am no mechanic) I believe Garrett or Mitts came out with a S/B on setting either the fuel flows or blade angles recently to help counter that.
Still,,,, a well seasoned and qualified pilot who knows the systems will be able to counter any rigging/setting/flow problem.
Just my .002 with a fair amount of Garrett time.

Hung

 

[siucavflight]

IMHO, no single engine should be allowed in commercial service at night, IMC or in icing.

Wow, I would hate to see that happen.

 

[Hung Start]

Well, if we put into our OPSPECS, as not allowed, it obviously cannot happen.
Why was this not thought of before????

Hung

 

[Rally]

As far as insurance goes. I have a '56 C-172 and a '54 C-170. Same exact airplane except for the position of the gears. Double the insurance. Lots of accidents in a C-170. It can be slightly tricky on occasion, but really when it comes down to it you just gotta steer and not let up on it. Probably the same way for the MU-2 in laymans terms. Problem is old habits die hard with the hold 3 degrees of bank etc into the good engine, according to what most people say your probably gonna end up in the dust.