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Prop wont restart in flight on FCF


angryjohnny
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Ok so flew FCF shut #3 down go to restart it the blades begin to come out of fleather just a tiny bit then go back to feather no propeller rotation. Land adjust NTS bracket go back up same thing ,go to Airstart prop begins to come out of feather a tiny bit then goes back to feather. this time change Valve housing perform run all checks good! back to FCF shut #3 down feathers fine go to restart, same thing comes out of feather just a bit then back to feather still no rotation of propeller need help with this one

I have a few theories one could be bad quad seals, not letting enough pressure to unfeather the prop with the extra force of 150 knots of wind another could be a weak aux feather pump motor doing the same last one is the pump housing is going bad?

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The indication of coming out a pit/tiny from feathered position, indicates a good initial unfeathering electrical circuits as well as hydraulic pressure and routing.

1-Why not the prop continuing the unfeathering cycle?

To me we should not track this issue; "Why not the prop continuing the unfeathering?" Based on:

Quoting: angryjohnny

The blades begin to come out of fleather just a tiny bit then go back to feather.

So: the dome quad seals leakage, and the Aux. Feather Pump weakness, etc.. are not our issue.

Our issue is:

2-Why the prop return back to feather and maybe up to the feather latch lock?

Which indicates, another feathering circuit is become active (electrical/mechanical) causing the "feather valve" to be opened.

A- Is it electrical feathering circuit malfunction?

might be, but, some malfunctions can be seen by the (pulling-In) of the feather override button during the malfunction, which is not mentioned in your post. And some possibility of malfunctions is located in the valve housing, which already had been changed. So what is left?

B- Mechanical feathering malfunction (NTS). The most likely

As mentioned by: pjvr99 Quoting: Check out NTS function on the RGB.

Note:

Good NTS operation during air start should act momentarily (pushing the feather valve to open) at initial rotation of the prop but not before and not continued. If NTS malfunction (over-act, sticky) it will keep holding the feather valve opened thus routing hydraulic fluid towards feathering. So keep tracking the NTS malfunction.

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(This is Mike Fisher -- I'm answering this from SonnyJ because we are TDY together) Is this a low time, high efficiency engine? A few years ago we were building compressors tight (blade tip to compressor casing clearance) in an attempt to improve engine efficiency - problem was that we were not doing a good job of measuring the clearance. We ended up with a lot of engines that were high efficiency but would not necessarily air start because when the engines were shut down the casing would shrink down on top of the blade tips. This was a significant problem on low time engines (< 200 hours) that we would shut down and immediately try to airstart (like during an FCF). We ended up having to produce a compressor seal break in procedure to get the engines to air start.

We thought we had eliminated this problem and have removed the compressor seal break in procedure but we are currently producing engines with 109 - 112% efficiency so it is possible that some of these engines will have the same problem. It sounds to me like the prop and NTS are doing what they are supposed to do. What I would recommend is to repeat the cruise engine shut down/airstart and if unsuccessful, leave the prop in feather for about 15 minutes and try again -- this will give the casing and rotor time to converge on the same temperature.

Mike F

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The prop brake is not allowing the propeller to rotate.

Use the starter (to release prop brake then release) to restart the motor..... The -1 in the AIRSTART section should have a note on the subject.

It should say something to the effect of ..... an emergency start can be attempted by using the starter IF there is blade angle change (which you have) and NO rotation...

Its NOT an emergency in fact it eliminates an energency!!!

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Quoting: (FM 382C-14E) section 3

If normal air start cannot be accomplished because of failure of the propeller to rotate, and blade angle change can be observed and is indicated by illumination of FEATHER VALVE AND NTS light, an air start may be attempted by placing the ENGINE BLEED AIR switch to OVRD and using the engine starter to help unlock the propeller brake.

1- To my understanding-and might be wrong-, that a “TINY BIT” change from 92.5 is not sufficient to blame the propeller brake, the brake to be released from a locked position required sufficient change of blade angle (to put the prop on the ram air force), beside it should be accompanied with illumination of NTS light, which is not stated and not the case of the defect.

2- Based on a couple of experience happened to me with propeller brake that failed to unlock during air start , the prop blade angle was clearly out of feather and never went back to feather.

But reaction might differ from system to system and I might be wrong.

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tenten,

Your right it does not say the NTS light was blinking... I would think the NTS was set correctly as the aircraft was on an FCF and the NTS check would have been preformed prior to the shutdown. Had it failed (no NTS) no shutdown would have bee done. But we will have to wait and see what johnny has to say...

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(This is Mike Fisher -- I'm answering this from SonnyJ because we are TDY together) Is this a low time, high efficiency engine? A few years ago we were building compressors tight (blade tip to compressor casing clearance) in an attempt to improve engine efficiency - problem was that we were not doing a good job of measuring the clearance. We ended up with a lot of engines that were high efficiency but would not necessarily air start because when the engines were shut down the casing would shrink down on top of the blade tips. This was a significant problem on low time engines (< 200 hours) that we would shut down and immediately try to airstart (like during an FCF). We ended up having to produce a compressor seal break in procedure to get the engines to air start.

We thought we had eliminated this problem and have removed the compressor seal break in procedure but we are currently producing engines with 109 - 112% efficiency so it is possible that some of these engines will have the same problem. It sounds to me like the prop and NTS are doing what they are supposed to do. What I would recommend is to repeat the cruise engine shut down/airstart and if unsuccessful, leave the prop in feather for about 15 minutes and try again -- this will give the casing and rotor time to converge on the same temperature.

Mike F

I see what you are saying here but was'nt most of those motors identified some 5 years ago and action taken ?

If so was this one of these motors and was a compressor break-in proceedure performed .

If it is one of these I don't care what aircrew is flying the bird you won't get it started even in bleed air over ride . The case shrinks too far and locks the compressor up. Ran into two of these compressors one at HS and another at the Deid. Both came back caged unable to start. And both were not indentified in time.

Best to bump the numbers on the compressor against you engine manager just for G.P.

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Yep I would recommend using the starter to help get the RGB to rotate if nothing else is working. Also you did not mention what KIAS you were at when attempting the Airstart. -1 recommends 180 IAS or less. If you are tring to airstart somewhere around 200 IAS the prop brake may be locked to tight to allow the prop to rotate.

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Wow, can't tell you how many times we saw this at Robins doing FCFs but since it's been a while now I'm not sure I can remember all the correctives. As has been mentioned using the Starter button to help override a possible tight prop brake is what to try first. I think the maintenance guys would "Flush" the prop brake if a restart could not be made.

Call the 339th Flight Test guys at Robins and talk to Scott Stansfield(heck he might be retired now) or Harry Smith in the FE section. Both those guys are top notch and may have better intel.

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Call the 339th Flight Test guys at Robins and talk to Scott Stansfield(heck he might be retired now) or Harry Smith in the FE section. Both those guys are top notch and may have better intel.

Harry retired last year. To bad too, he was one of the finest FE's I ever dealt with. Scotty is still there. I don't recall ever flushing a prop for this problem at Functional. The only times something like this has happened it was either the valve housing or Prop housing I beleive. Flushing is typically done when the prop spins backwards.

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Harry retired last year. To bad too, he was one of the finest FE's I ever dealt with. Scotty is still there. I don't recall ever flushing a prop for this problem at Functional. The only times something like this has happened it was either the valve housing or Prop housing I beleive. Flushing is typically done when the prop spins backwards.

Oh yeah I forgot about the spinning backward! We had our share of them too. I didn't know that Harry had retired but I don't keep up with the guys. Just chat with Scott occasionally.

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Just supporting Mikes response. If this is a rebuilt engine then bumping the starter will not help. you simply have to wait about 15 minutes (as Mike stated) until the compressor cools and the blades cool which will reduce the clearance and allow the compressor to rotate. Once you get the airplan on the ground their was (about 5 years ago) a Maintenance procedure for breaking in the engine which amounted to starting and shutiing down the engine multiple times

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Just supporting Mikes response. If this is a rebuilt engine then bumping the starter will not help. you simply have to wait about 15 minutes (as Mike stated) until the compressor cools and the blades cool which will reduce the clearance and allow the compressor to rotate. Once you get the airplane on the ground there was (about 5 years ago) a Maintenance procedure for breaking in the engine which amounted to starting and shutiing down the engine multiple times

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As brothers mentioned that a “Compressor Tight Engine†is one possible cause of the defect. (engine failed to rotate during air start).

The question for brothers having experience on “Tight Engines†is; such engine; dose it show some indications during ground check?

Such as:

1- Repeated failure to rotate during start, when still hot.

2- Repeated starter failure.

3- Above 100% efficiency.

6- Visual evidence of “Rubbing†on the compressor blades tips (fifth & tenth stages compressor check).

7- Rubbing noise during “hand rotation†when engine still hot; etc…

For the sake of knowledge, comments will be appreciated.

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As brothers mentioned that a “Compressor Tight Engine” is one possible cause of the defect. (engine failed to rotate during air start).

The question for brothers having experience on “Tight Engines” is; such engine; dose it show some indications during ground check?

Such as:

1- Repeated failure to rotate during start, when still hot.

2- Repeated starter failure.

3- Above 100% efficiency.

6- Visual evidence of “Rubbing” on the compressor blades tips (fifth & tenth stages compressor check).

7- Rubbing noise during “hand rotation” when engine still hot; etc…

For the sake of knowledge, comments will be appreciated.

1010

Over the years had a number of high performers up to 113%, but none of the problems you

mentioned. We simply followed the seal break-in procedure in TO 2J-T56-56 SWP 058 03 Sect 13

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