Rocket Cowl Flap Motor

[David Mazer]

Anybody know anything about converting from the electric cowl flap motor to a manual cable control for a Rocket?  My motor burned up and the thing costs over a $1,000, isn't in stock, and seems to burn up often.

Thanks.

[RJBrown]

An 86 rocket is a 252. The earlier 231 based Rockets use a cable. All the parts are different from the cowl to dash. I don't think you can get there from here. Sorry.

[fantom]

Pull that little motor out and any good mechanic should be able to clean it up and rebuild it for no more than a couple of hundred bucks.

[David Mazer]

Thanks for your input on this.  I didn't realize the 231 and the 252 Rocket cowl flaps were different.  My Rocket looks like the cowl flap motor is a modification so I expected the 231 and 252 versions to be the same in that respect.

I have a mechanic looking at it this week but his experience is that somehow the gears were stripped and the rebuild is more expensive then a new one.  I suppose I will learn more about this later this week.

Thank you both.

[David Mazer]

Spoke with Rocket Engineering today and they told me they didn't put in the cowl flap motor.  The 231 Rocket is cable operated and the 252 is electric.  So, I spoke to Mooney to see if a 231 cable would fit into a 252.  Their answer was no way.  Of course.  Back to square zero (haven't managed to get to square one yet).

[KSMooniac]

I believe someone (maybe Mod Works) had an STC to use a vernier control on cowl flaps, but I can't remember if that was to replace the simple push-pull cable or the electric motors.  You might fish around and see if you can find it on the FAA website...

Failing that, if it were me, I would try to gain a 337 field approval for such a swap and think it should be fairly simple since it doesn't really involve any structure, flight controls, etc.  Of course this depends on your local FSDO and IA, but I think it would be worth the effort to get rid of an expensive and heavy electric motor for something simple, reliable, and lighter weight.

[KSMooniac]

dp

[snowds]

Any luck on this project?  I have a 231 Rocket with a bad cowl flap cable, and apparently there are no new OEM cables available anywhere.  I've heard of people putting in a vernier cable under a 337, but haven't actually met anyone who has done that.

Stephen

[danb35]

Can you have McFarlane make a duplicate of your cable?  That should be installable as an "owner-produced part" if your A&P will agree that copying the dimensions of your cable is enough "approved data" to make the part.

[David Mazer]

It looks like I will be putting in a cable to replace the motor under a 337 next month.  I will report how it goes then.  Sorry for the long delay but I have been working on this for months already.  I'm sure you all understand how long these odd projects can take.

[donshapansky]

I would think you must have some other issues going on, I have the same model with the Rocket STC, over 700 hrs without any motor problems. I just touched some wood to remove the jinx.

 

[David Mazer]

I do, or did.  Two A&Ps have told me the cause is someone putting the lower cowl on incorrectly causing the gearing to strip.  Unfortunately, those two A&Ps were the only two people that had taken my cowl off and back on since its last annual when it was noted to be working.

Word to the wise - check your cowl flap condition after each time the lower cowl gets reattached.  At least you will know who is responsible.

[David Mazer]

Well, here is a picture of the new manual cowl flap control.  Works great on the ground.  Unfortunately, not so good in the air.  The manuals mention the need to close the flap as you arrive at altitude as the air flow tends to pull the flap open and the manual is right because I can't seem to pull this closed in flight.  I tried slowing down to about 120 kts but that didn't help either.  The installer is aware of the problem but

doesn't have a ready answer yet.

If anyone knows any easy answers, I'd appreciate it.

[aviatoreb]

Quote: Mazerbase

Well, here is a picture of the new manual cowl flap control.  Works great on the ground.  Unfortunately, not so good in the air.  The manuals mention the need to close the flap as you arrive at altitude as the air flow tends to pull the flap open and the manual is right because I can't seem to pull this closed in flight.  I tried slowing down to about 120 kts but that didn't help either.  The installer is aware of the problem but

doesn't have a ready answer yet.

If anyone knows any easy answers, I'd appreciate it.

[David Mazer]

The cooling, and the cowl flaps, are more important above 16,000 ft.  My high altitude climbs usually include a reduced climb above 16,000, say 600 ft/min from there on, and an occasional respite at that altitude for a few miles and then resumption of the climb.  Also, my ambient temperature in FL is probably higher than yours.

Do you have a picture of your cowl flap actuator?

[aviatoreb]

Quote: Mazerbase

The cooling, and the cowl flaps, are more important above 16,000 ft.  My high altitude climbs usually include a reduced climb above 16,000, say 600 ft/min from there on, and an occasional respite at that altitude for a few miles and then resumption of the climb.  Also, my ambient temperature in FL is probably higher than yours.

Do you have a picture of your cowl flap actuator?

[David Mazer]

Yes, the lever in the cockpit.  Thanks.

[RJBrown]

Cooling was never an issue with the 1980 231/Rocket I flew for 1000 hours. Yes the cowl flaps are impossible to move at speed. Full open before you start the roll. Climb fast like a turbine and close them as you level off and before you accelerate. Set up properly the flaps never fully close. They are "in trail" when closed. I have climbed directly to 26,000 still over 1500 FPM with no heating issues. The change from the 231 to the Rocket was amazing. The 231 never cooled well, the Rocket never ran hot. 

 The metal angles at the cable attach is bent sheet metal. It is too light for the job. It can bend so far you will go way over center on the mechanism when you open the flaps and you will be unable to close them at all. Wide open they really cost you speed. I got used to checking the shape of those parts regularly. To stay open with the wind they need to be just a touch over center. As you push they open a bit before they close. Too far over center and they are hard to close, way too far over center and they won't close. Trying to open and close at speed bends these parts. This is something that you as the pilot need to understand and adjust. I thought of machining a block of aluminum to replace the piece that bends but never did.

 With the flaps in trail you can cruise climb without over heating. If center gives a climb of 2000 ft you can just trade speed for altitude and zoom climb. Before you get too slow or raise the temps you are 2000 ft higher.

[aviatoreb]

Quote: RJBrown

Cooling was never an issue with the 1980 231/Rocket I flew for 1000 hours. Yes the cowl flaps are impossible to move at speed. Full open before you start the roll. Climb fast like a turbine and close them as you level off and before you accelerate. Set up properly the flaps never fully close. They are "in trail" when closed. I have climbed directly to 26,000 still over 1500 FPM with no heating issues. The change from the 231 to the Rocket was amazing. The 231 never cooled well, the Rocket never ran hot. 

 The metal angles at the cable attach is bent sheet metal. It is too light for the job. It can bend so far you will go way over center on the mechanism when you open the flaps and you will be unable to close them at all. Wide open they really cost you speed. I got used to checking the shape of those parts regularly. To stay open with the wind they need to be just a touch over center. As you push they open a bit before they close. Too far over center and they are hard to close, way too far over center and they won't close. Trying to open and close at speed bends these parts. This is something that you as the pilot need to understand and adjust. I thought of machining a block of aluminum to replace the piece that bends but never did.

 With the flaps in trail you can cruise climb without over heating. If center gives a climb of 2000 ft you can just trade speed for altitude and zoom climb. Before you get too slow or raise the temps you are 2000 ft higher.

[David Mazer]

Finally have a working cowl flap.  Finally.  The first cable was replaced with a heavier cable that is lockable at various positions allowing infinite adjustments like the motor was supposed to do.  Sorry that one of the pictures is blurred.

[goncaloareia]

Hello all!

Our Mooney 252 had a working cowl flap engine actuator until last week, when it went to the avionics shop, the guys removed the lower cowl, putted everything back on when they finish, and now... guess what... the cowl flap motor is malfunctioning....

They removed the motor, and told me that the electric part of the motor is fine, but the shaft assembly and specially the secondary shaft that connects to the gears that multiply the motor force is worn out and also loose. They tried to grip it back in place with no success...

I'm now seeing some 1.300 USD as the lower price I can find for the stupid small motor...

Any ideas of how to repair (if its possible) this motor and its gears/shafts?

Any clues of how easy/cheap it could be to put the cowl flap control manual?

And one last question: we are afraid of flying with the cowl flap motor inop because the cowl flap moves almost freely from open to close, and it closed somewhat when we did a run-up test this morning.

Do you guys know if the cowl flap will open or close in flight?

Thanks for the help and best regards to all.

Goncalo Areia

Lisbon, Portugal

[N601RX]

You can get a new motor or have yours repaired a Globe Motors in Dothan, Al. Ask for the FAA repair station.

[David Mazer]

Gancalo,

 

For the record, my problem is still not fixed.  I have a workable solution but it isn't what I would like.  The damage you note may be the exact damage I have been told can't be fixed.  There are two or three places that will repair these depending on the manufacturer of the motor which, apparently, can vary.  Replacing the motor, if you can get one, will not guarantee that the problem won't happen again immediately.  If you have found one for $1,300 it is 30% higher than Mooney quoted me but they also said they didn't have any in stock and didn't know when they could get one.  This was a very poor design and the removal and installation is a real pain on my Rocket.  It may be easier on a 252.  I have tried converting to a cable system with limited success.  The forces are just too great at cruise speeds.

 

As far as is ti safe, I sure hope so.  I've been flying for a few years with no control over the cowl flaps and haven't had a temperature issue.  I do believe it is costing me a couple kts but I'm not certain.

 

Before you go through everything I have, PM a time when we can talk.  It will be much more efficient.

[goncaloareia]

Thanks for the tips!

This cowl flap issue sure looks like a bad design from Mooney. No wonder they've changed it in more recent models, or skipped the cowl flap totally!

David, I'll PM you after getting more news tomorrow from the A&P shop and have more clues on the various solutions that we can have for this.

Goncalo

[David Mazer]

Actually, the design before (231) was better and it was the "improvement" that was a problem.  The 252 arrangement can't even be easily converted to the 231 model because parts required for bracing aren't there on the 252.  We'll talk more when you are ready.