I had a hydraulic line on the gear of a piston commander blow on gear retraction.

I was actually watching it when I selected the gear up. It had just been repaired due to a leak.

All I had to due was slow to about 100 kts and the gear slowly locked into place.

The system is hydraulic/pneumatic meaning every time you use the system both the nitrogen and the hydraulic is helping extend the gear. If you lose fluid you lose the assist of the fluid but the pneumatic system coupled with the bungee system is enough to extend the gear. As long as you slow the plane down.

Nothing violent about it.

There is a hydraulic actuator and a pneumatic actuator.

The bungy gets changed every annual or every 100hrs if you're on the factory program.



Yeah, gear goes backwards and twists 90 degrees to fit flat into tapered nacelle. It's all done completely mechanically with an angled shaft at top of leg, so it self actuates on extraction/retraction. It's actually a kind of cool design - someone got clever at the drawing board that day.

The design of the gear system in the Merlin is something that I really admire. It is very simple yet effective. It is hydraulic with a standpipe inside the hydraulic power pack. If bust a line and fluid escapes there is enough in the standpipe to work the gear. Additionally, since the gear raises forward the emergency extension is a simple cable unlock release and gravity free fall. When the massive gear leg starts to fall it catches the wind and is locked and down in a short time.

Steve, that is a very nice Commander and one to be proud of.

yes, I have Commander Envy...


(and congrats on the 1000 post count, Steve)

Beautiful Commander Steve! I really like your panel and how well it turned out. Congratulations.

Commanders also have a standpipe and a shorter one for the aux pump so a technique for backup is to shutoff the aux pump so you have some fluid remaining for brakes, etc. In the case of a leak. Anyway, there is no nose uplock other than hyd pressure so when you lose pressure you can hear it via the nose wheel springing down and locked. I have lost pressure one time in about 6,000 hours. That event was on a mx test flight after the plane had trashed hyd pumps previously. I can't recall what caused it. I did need to slow down to get 3 green.

Congrats Steve!! That is one sweet looking Commander. Definetely the nicest Twin TP´s produced. This one looks as if it came out of the production line!

* How come the MU-2´s have put the five bladed MT Props and these have not been approved / installed in the Commander´s? That would bring a LOT of stance in these machines and maybe some improved performance...

Because the plane showing off the first install crashed from an inflight break up. it was 10 years ago.

http://www.ntsb.gov/_layouts/ntsb.aviat ... 004&akey=1

If you fly a Commander, and it is bumpy, you need to slow down.

I hear rumors the MT prop project for Commanders may return at some point.

Mike C.

Because the plane showing off the first install crashed from an inflight break up. it was 10 years ago.

http://www.ntsb.gov/_layouts/ntsb.aviat ... 004&akey=1

If you fly a Commander, and it is bumpy, you need to slow down.

I hear rumors the MT prop project for Commanders may return at some point.

Mike C.

No STC for the 441 listed on MT web site, nor any project to do it that I know of.

It would be a good fit for the 441. The original prop is 90 inches diameter, and the 5 blade MT replacement would be 82.6 inches diameter. This would add 3.7 inches ground clearance, something the 441 could use as it doesn't have much to begin with (10.2 inches according to the AFM).

The Commander and MU2 are high wing, so prop is well off the ground. Merlin has tall gear, so not as affected.

The other benefit is slower tip speeds reduce noise, and further away tips reduce noise as well. 5 blades makes the noise different tone, somewhat more even, less rumbly.

I spoke with the person who did the MU2 MT prop STC and asked if they would be interested in doing the 441. He said bring him a plane and they will do it.


Not with an MT that I know of.

The 441 had the bad tail problems very early in its service life that led to horrific crashes, groundings, and new tails. After that, the 441 has been pretty good mechanically.

Mike C.

Classy posts from the wiki notwithstanding, the props did not perform well enough according to the test pilot who told me directly. Same with 4 blades which I tried. Add vibration and aerodynamic challenges without significant performance increase and you have lack of interest. Nothing worked as well as a Hartzell 3 blade wide chord q tip. Maybe a new prop will develop in the future.

The MT 5 blades props tend to increase performance for takeoff and climb, be neutral or slightly negative for cruise, like 1-2 knots. Owners who switched universally like them. Aesthetics may be a big part of the equation.

There is a weight reduction, 22 lbs, small but something. Noise reductions are claimed to be 8 dB, which is perhaps stretching it a bit, but the MTs are definitely quieter.


Owners who switch to 5 blade MT report less vibration, smoother, quieter. The fiberglass blades tend not to "ring" like the metal ones.

There is some concern the deicing of the MT might not be adequate because it vibrates so much less. On the metal blades, this vibration on the outer 2/3rds of the blade helps sheds ice (which is one reason the deice boots don't extend out further). The less vibration MTs may allow more ice beyond the electric boot.


If cruise speed is your only metric, I agree. Fewer blades will perform better, though the difference is fairly small and hard to measure if the props are given equal effort at optimization. MT will claim a cruise speed increase, but I don't believe that is true, and it could be slightly negative, but perhaps immeasurable in actual fact.

Mike C.

the best prop upgrades are those that eliminate a recurring (read expensive) AD

That is true for the slow turn MU2s with the original Hartzell props, and is a motivating factor in choosing the MTs for those. The AD requires a 5 year inspection process which is so invasive that it is pretty much an overhaul. Many are getting an AMOC to extend that to 7 years.

Do the Commanders have a similar AD? I didn't think so but I could be wrong.

Mike C.