The International Cessna 170 Association

I reached out to MT Propeller thru email giving specifics of my plane and asking if they had a constant speed propeller that they would recommend. Additionally if they would be willing to provide/assist with engineering data in an effort to get a DER to process the proper paperwork to give to a DAR in hopes of a one time field approval.

Surprisingly they responded fairly quickly with their recommendation of CS Propeller and willingness to help with the process. MT went so far as to point out they know a DER who could possibly help as well

Do I think this would be a quick easy process, no. But the possibility does exist to put a quality CS Propeller on our C-145 O-300 powered 170’s.

Now the reality. They are ridiculously priced. Also MT wants an order to start the process. I emailed them about possibly making a refundable deposit if after a year no approval has been received. But told them I was unwilling to spend $15,000 plus taxes on a propeller that could become useless wall art.

There is a DER who lives 10 minutes from me. When I was working on my 170A he stopped by to introduce himself and visit. He’s a nice guy who offered help if I ever needed it.

Has anyone been down this road already with MT and the FAA.



Email from MT
“We know a  FAA DER and he can possibly help to do the field approval.

The propeller we propose is our 74 inch diameter 2-bladed

MTV-17-D/188-17f        USD    9.600,-
Composite Spinner        USD    1.550,-
Spacer P-670-8-60        USD    1.000,-

Control Unit
P-120-U/2700, 12 VDC    USD    1.900,-

All prices are ex factory without VAT.

You need a manifold pressure gauge and a 4 Amp circuit breaker.

Please confirm that the spinner P-945 is compatible.
All dimensions are in mm, if you divide by 25.4 you get inches.

Thank you for the interest and please let me know if you like to order.

Best Regards
MT-Propeller Entwicklung GmbH

Martin Albrecht
Vice President/General Manager”

I think about going down this route occasionally.

But, I have not been willing to be the guinea pig....

I would be sorely tempted if there was a sure path to approval.

Jim,

It doesn’t sound like there are ANY 170s flying anywhere in the world with that propeller on an O-300?

I don’t worry about being a Guinea pig. I just don’t wanna put that much money into a slim at best chance of it going thru. I also realize there are no 170’s with that set up. But wouldn’t it be fun to be the first.

I’m hoping they will accept a deposit as a good faith showing and get their known DER to work.

There’s no doubt in my mind that it can be done, but I would like to understand how they propose that the propeller would work and be controlled on an engine with no oil supply to the propeller, and no provision for an engine-driven governor.

Also, it might be a good idea for a moderator to separate this out into a separate thread. <Done - Moderater

cessna170bdriver wrote:There’s no doubt in my mind that it can be done, but I would like to understand how they propose that the propeller would work and be controlled on an engine with no oil supply to the propeller, and no provision for an engine-driven governor.

Also, it might be a good idea for a moderator to separate this out into a separate thread.

Link:http://www.mt-propeller.com/en/entw/pro_elec.htm

Agree on separating the topic. And Jim how about posting a link to that other electric prop we talked about whose name I have already forgotten. <Done - Moderater

Miles, it’s an electrically controlled propeller. Has mechanical fine and course limits. The actuator as I understand it is a certified actuator that is used in a pressurization system in one of the big planes. Even if the controller or actuator runs away the mechanical limits will keep it with in limits. In a 310 years ago I had a governer failure that put one side the the fine limit while the other side worked fine. So I finished the trip with both side in fine pitch and power pulled back. Was a slow ride, but uneventful.

Paul. The other one was Airmaster Propeller. I backed off of them because they are experimental and doubtful it could get through the process. I still think it’s a good piece. This was their recommendation.

http://www.airmasterpropellers.com/ap533ctf-wwr72a

Thank you Paul and Jim. I figured that the propeller would have to be electrically actuated, and I was aware that MT Propeller was out there, but I wasn’t aware that they had developed a certified electric propeller.

Jim, I assume the “spacer” mentioned in your price list is the interface that gets you from our 8-bolt propeller flange to whatever the MT hub is? Do you have any idea what the weight and CG change would be for this propeller?

If you assume a 30 takeoff horsepower increase, $15K is on par or somewhat cheaper per horsepower than dropping $30-40K on the 65 hp increase a 180 Lycoming upgrade gives you, assuming of course that the DER won’t charge another handful of AMUs for the approval. I have a pretty good relationship with a couple of FAA types here on the field, so I could talk to them to see what to expect in the approval process.

The prop suggested would have a 2 inch reduction from a standard FP prop. Sounds like more spin for horsepower but less pull, overall performance might not be that great.

c170b53 wrote:The prop suggested would have a 2 inch reduction from a standard FP prop. Sounds like more spin for horsepower but less pull, overall performance might not be that great.

I think the fact that the prop is constant speed will make up for most of that. Blade design has a lot to do with it too. When using a Hartzell blended airfoil constant speed propeller, Vans recommends a 74-inch for the nosewheel RV-7A, and a 72-inch for the tailwheel RV-7, and claim no loss of performance. On the O-300, we won’t know until someone tries.

If you look at the AFM, the approved Sensenich propeller is 74”.

The already-approved 2-speed McCauley is also a shorter/smaller diameter. If the MT prop is similar in performance to the 2-speed I'd never spend $15K for that small increment of performance.

We like to dream...but one reason the 170 is such great little airplane is because of it's relatively inexpensive operation. A special prop takes away from that feature. (One of the reasons I sold my beloved 206 was the expense of operation when most of my flying was solo or one other person operating off a 3,400' strip. All I actually need 99% of the time is to get airborne in a couple thousand feet and fly 120 mph.)

Doesn’t really matter anyway as this morning I received a response from MT that they infact want the full cost paid up front. Told them no I would not be willing to do that and explained that the FAA actually cautions not to buy anything until all the paperwork is done and approved.

It’s a shame cause it’s a simple system from a good company and in my opinion would be a good added feature. I’ve flown with both a climb prop and a speed prop. This would give benefit of both with out the hastle.

George, your right, the 170 is very basic and simple in nature from a time that was the same.

Thanks Ryan, as usual just thought it was 76" without verifying and I guess Miles said it best, who knows until you try.

Guess that explains why no one has it on a C170!

Seems like their business model is kind of self-limiting, but apparently they have all the business they want!