Rocket - Fuel Vaporization?

[Jeff H.]

Hello All,

 

First, thank you to all who have unknowingly provided an information treasure trove which helped drive the decision to purchase my first airplane - 1981 M20K Rocket.  I've had a lot of questions, however most have been able to be answered by searching this site.

 

Now that I actually have the Rocket, I have the usual long question list.  The first being that on the first landing at the home airport the engine stumbled in the pattern and then quit on roll-out.  We were able to recreate the problem this weekend:

 

- 20" MP or less

- Intermittent stumbling.

- Shadin fuel flow goes from about 14 to 5 and then recovers.

- Occurred at 5K altitude while practicing configuration changes and approaches.

 

Suspect fuel vaporization.  Any thoughts on why this would be occurring at low altitudes or other likely issues?  Is this a common Rocket issue and just hit low boost pump and move on?

 

On other new ownership issues - seemed like we had a squelch issue on the intercom.  Convinced there was an avionics issue.  You know, until I moved the vent from blowing on my mic.  Ah yes, this is going to be fun.  :-)

 

Thank you for any insights,

 

Jeff

[RocketAviator]

I have never had anything like you describe in my Rocket. 

Would personally be a little concerned if it were me, the last place you want your engine to stumble is low altitude, landing etc...

I do not use the fuel boost and other than engine failure or high altitude I do not believe my POH addresses the need / use of fuel boost.

I read a 2012 MS forum "Function of my Boost Pumps" where aviatoreb and some others talked about the fuel boost topic in some details.

 

I hope you enjoy your Rocket as much as we enjoy ours.

Fly safe,

[Houman]

Hi,

 

Welcomed, I'm also a new Rocket owner, bought it couple of months ago, I did have issues hot starting the Rocket and it was due to fuel vapor, I followed the procedure found on this site and it works perfectly. I will be uploading my personal check list here so it might be of help to you as well.

 

As for the engine issue, I have never had that, how many hours do you have on the engine, mine has about 170h on it now, so it is practically new and as RocketAviator said, I would really be concerned if this happend in the patern or low altitude, something you would want to have looked at.

 

Enjoy the Rocket !!!

[Seth]

Jeff-

I do not have the Rocket but I have the other Mooney to come out of Rocket Engineering; The Missile. It's a normally aspirated IO-550 rated at 300 HP as opposed to the turbo version (the Rocket).

I had a similar issue when the engine was at idle after the overhual of my engine. When on final if I was properly configured, the engine would stumble when I pulled the power to idle. Once it actually died on me on roll out on the runway.

When the engine was remounted and the idle full mixture was set, it was too much flow and would cause the engine to flood. Once adjusted, this was no longer an issue at idle - as the amount of fuel at the full mixutre low idle setting is no longer flooding the engine and causing it to die. However, the new issue is that when the low idle mixutre is alterted, it changes some sort of bladder which also affects the full power mixture setting. Thus, my full rich mixture high power setting was lowered and I was cooking my cylinders at high power settings. It's an adjust, test, and readjust procedure until you have the correct low power full mixture and the correct high power full mixture.

Until you have this resolved, simply lean on downwind so that you're engine doesn't gurgle/flood on final when you pull power out. Just remember ot push the mixutre level full forward on go around!

This could be the issue - it may be somthing else - have the full mixutre low power and high power bladders checked and adjusted.

Take care,

-Seth

[David Mazer]

Glad to hear Formation HY had success with the hot start procedures.  It works for me every time.

 

Jeff H - yikes!  Not a Rocket issue as far as I'm aware.  I did know of a 252 that had an engine failure while turning right during taxi.  As odd as that may sound, it was a known problem and solvable.  I'll see if I can find the information about that for you tomorrow.  Yours may be some variant of that but I'm pretty sure it would take a real emergency to get me in the air with that problem unresolved.

[Alan Fox]

Does the amount of fuel in the tanks coincide with the stumble??  Turns??  at low fuel levels , it is possible to "unport" the fuel in the tanks.....

[carusoam]

Vapor lock is the cause of failed hot starts...

Vapor lock is an issue caused by heat while the engine sits. The fuel in the lines gets heated and has time to vaporize.

It should not be confused with something that happens while the engine is running. Certainly not while the plane is flying.

This would be an unacceptable design as it would lead to too many off field arrivals.

If you have seen the FF varying in an uncommanded situation. You have enough detail to visit with a mechanic.

Keep in mind, I am only a PP. But it sounds important enough to speak up...

Best regards,

-a-

[chrisk]

Vapor lock is the cause of failed hot starts...

Vapor lock is an issue caused by heat while the engine sits. The fuel in the lines gets heated and has time to vaporize.

It should not be confused with something that happens while the engine is running. Certainly not while the plane is flying.

This would be an unacceptable design as it would lead to too many off field arrivals.

If you have seen the FF varying in an uncommanded situation. You have enough detail to visit with a mechanic.

Keep in mind, I am only a PP. But it sounds important enough to speak up...

Best regards,

-a-

 

At one point I thought about getting into a Cessna 210.  They have a reputation for vapor lock with the engine running. --Well the engine running before vapor lock stops it.

http://www.37000feet.com/report/362421/Report-concerning-the-CT210-problem-of-vapor-lock-even-at-high-altitude

 

As far as your Rocket, I'm guessing an overly rich mixture at low RPM and power settings.

[aviatoreb]

Anthony is right - this is not vapor lock.

 

I like Seth's theory.

 

I have not had this problem - knock on wood.

 

This is not a problem to take lightly - not that you are.  I do know that after Dorn from Weber in Lancaster flew my airplane once he said it was especially nicely setup and smooth at all settings - he mentioned that he had recently seen a rocket that was cutting out on roll out just as you describe.  I think they cured that airplane.  Maybe give them a call?  In fact I dropped my airplane off there today (for other issues like a landing hear switch and a tight trim wheel - its like dropping your airplane off at the "spa").

 

(Hey Seth - last time I dropped my airplane there - you were right behind me - will we have lunch this time?!!!)

 

Good luck!!

[Piloto]

Sounds like a fuel pump diaphragm leak. On the ground (engine off) set throttle and mixture fully open. Turn electric fuel pump on. Let fuel pressure build up. Close throttle and mixture while the pump is running. Turn pump off. If the pressure drops within 10 seconds it is likely due to a fuel leak between engine pump and the fuel servo or the pump internal diaphragm is rupture. Check engine fuel pump vent line for fuel leak.

 

José

[carusoam]

ChrisK,

Proof that the M20 is a better design than the C210!

-a-

[Jeff H.]

All,

 

- Aircraft was just out of annual when purchased.  Timing was adjusted from 25 to 20 degrees.  Possible affect on proper idle mixture settings?  (What worked before doesn't now?)

- Signed up for SaavyMX as a new plane owner felt it would be helpful.

- Last week downloaded and sent to to SaavyMX 25 hours of flight data from JPI 700.  They confirmed the stumbling and suggested fuel starvation based on temps.

    - Will possibly have a SaavyMX pirep after working through this.

- First occurrence was after 10 hrs flying and a 4 hour leg.  Validated the Shadin fuel remaining values, gauge values and gas in tank after filling this weekend.  Had 7+ gallons remaining in the selected wing tank, so should not occurred because of low fuel.

- Yes, my confidence level in the plane was very low when we departed over the weekend.  Took things very . . . slowly.

 

Seth:  Thank you.  Saavy noted that the take off CHT values were higher than what they wanted to see.   Interesting coincidence.

Jose:  Thank you, I will run the test.

David Mazer:  Using your Rocket checklist exemplar and making changes for my specific aircraft.  Thanks for posting.

 

Thank you to all for the insights.  I do appreciate it.

 

Jeff

[Guest]

Jeff,

The timing setting of 25 does not sound right. If your engine is a TSiO 520 NB as removed from a Cessna 340, the SB says 20 degrees, not 25, so unless Rocket Engineering spec'ed it to 25 you maintenance is wrong. There is a TCM S/B relating to the subject, search TCM SB 94-8D.

Also look into S/B 97-3E on proper fuel injection set up. TCM uses a positive displacement pump, no diagrams to leak, just a number of adjustments for idle fuel flow, idle speed, maximum boost, maximum fuel flow, maximum RPM. A bit of work to set up, not a job for the un skilled though.

Clarence

[Seth]

Anthony is right - this is not vapor lock.

I like Seth's theory.

I have not had this problem - knock on wood.

This is not a problem to take lightly - not that you are. I do know that after Dorn from Weber in Lancaster flew my airplane once he said it was especially nicely setup and smooth at all settings - he mentioned that he had recently seen a rocket that was cutting out on roll out just as you describe. I think they cured that airplane. Maybe give them a call? In fact I dropped my airplane off there today (for other issues like a landing hear switch and a tight trim wheel - its like dropping your airplane off at the "spa").

(Hey Seth - last time I dropped my airplane there - you were right behind me - will we have lunch this time?!!!)

Good luck!!

Unfortunately not today - I'm in DC/MD not flying up to LNS - but let's coordinate sometime for lunch!

[Seth]

All,

 

- Aircraft was just out of annual when purchased.  Timing was adjusted from 25 to 20 degrees.  Possible affect on proper idle mixture settings?  (What worked before doesn't now?)

- Signed up for SaavyMX as a new plane owner felt it would be helpful.

- Last week downloaded and sent to to SaavyMX 25 hours of flight data from JPI 700.  They confirmed the stumbling and suggested fuel starvation based on temps.

    - Will possibly have a SaavyMX pirep after working through this.

- First occurrence was after 10 hrs flying and a 4 hour leg.  Validated the Shadin fuel remaining values, gauge values and gas in tank after filling this weekend.  Had 7+ gallons remaining in the selected wing tank, so should not occurred because of low fuel.

- Yes, my confidence level in the plane was very low when we departed over the weekend.  Took things very . . . slowly.

 

Seth:  Thank you.  Saavy noted that the take off CHT values were higher than what they wanted to see.   Interesting coincidence.

Jose:  Thank you, I will run the test.

David Mazer:  Using your Rocket checklist exemplar and making changes for my specific aircraft.  Thanks for posting.

 

Thank you to all for the insights.  I do appreciate it.

 

Jeff

Seems to me, of course after ruling out the test Jose suggested, that your mixture settings are simply off.

 

From what I was told it's a bladder system that controls how much fuel flows at what mixture and power setting.  Again, be careful to check the full rich high power and full rich low power settings.  Enough to keep the engine running without flooding it on the low power setting and enough fuel for our thirsty engine at takeoff power.

 

We had another Missile owner on here where the setting was not correct on the high power takeoff setting and he ended up needing a Top OH to fix the fried cylinders.

 

-Seth

[aviatoreb]

Unfortunately not today - I'm in DC/MD not flying up to LNS - but let's coordinate sometime for lunch!

 

Check pm.

[KevinR]

Hi All, I joined the New Rocket Owners Club two weeks ago. +1 on the hot start protocol & checklists. Thanks! Definitely interested in Savvy pirep as I expect to be away from home base often.

I have an EDM 700; has anyone been able to download data to a windows 8/ MSFT surface pro?

Just completes an extensive Maxwell annual- excellent experience. Had a fuel controller leak/ rebuild so I'll be happy to post engine data for Rocket comparison as soon as I can get the data out of the panel.