I'm not sure who to believe

[Eraaen]

I have owned my 80 231K/Rocket for about 5 years now.  I have NEVER seen Fuel Flows at the level they should be.  Maxed out around 27gph on full power.  I have mentioned this every oil change/annual.  I was always told it was within specs.  Well, the last few flights it never came above 23gph.  I mentioned this again.  Time to send fuel pump out (fine) a new/rebuilt one comes back.  Now fuel controller is dumping gas.  It goes out (fine).  All put back together and log notes state totalizer is showing 5GPH high.  I scratch my head.. NO WAY.  It's been spot on for 5 years (even had a conversation about it with maint. manager)  I was shown the certified gauge they used to set it up.  He says, "keep an eye on it and let me know."

I decide it's best for me to go solo on this one.  I enter the runway and slowly push up the manifold pressure.. the fuel flow keeps climbing and climbing at gets to around 39gph. (they did say it was showing 5 gph high)  But, I am hauling A** and by this point very far behind the aircraft and decide its time to stop watching and start flying.  Well, I'm well down the runway and moving fast, so when I rotate I blast off!! and that's when the motor just went BLAAAAHH.  I made the immediate decision that I was not ending up on the other side of the fence.  In one swoop I had pulled the power, put out airbrakes, and put the plane into one of the wildest slips you would ever see this close to the ground, while at the same time dropping flaps.  I hit the ground just as I rolled out of the slip.  Had to commit to another decision.  If I went off the end of the runway, into the grass/downhill, I'd loose all braking force and still be in the fence.  So I got as far to the right as possible and cut the left corner off the runway with tires screaming.  I fully expected to hear metal crunching as wing hit or gear collapsed.  I got it stopped in the staging area. Then realized the motor was running fine.

So, obviously. My gauge is fine and I totally flooded the motor on takeoff.

After some extremely direct "conversation" with the Maint. Manager.  He offered to purchase a new gauge and look at it.  Just got a phone call.  The rebuilt core housing is bad and wont let the set screw hold the adjustment screw in place.  So, it was backing out and increasing the pressure.  They had it set correctly in the hanger but,  when they buttoned everything up and did a final run the totalizer showed 5 high, because.. it was after the adjuster backed out.

I'm not really sure what the moral of this story is.  It should NEVER have left the rebuild company like this.  My guys SHOULD have caught the problem.  I SHOULD have insisted on more follow through/testing before attempting to fly.  Just sharing a story, because it was scary.

[gsxrpilot]

Damn!

[kortopates]

Thanks for sharing your horror story! Who did your CMI pump rebuild? Did they bring it up to the latest pump configuration for your TSIO-520 called out by CMI? 

Your story is a good lesson/reminder for many that think its okay to load the family up or depart IMC right or even for a long x-ctry flight right after extensive maintenance when really a maintenance flight is is required to prove the aircraft is all okay first. Ground run ups only go so far.

[charlesual]

Holy moly!!. I probably would have done the same. FWIW, I probably would have done the same.


Sent from my iPhone using Tapatalk

[Eraaen]

2 minutes ago, kortopates said:

Thanks for sharing your horror story! Who did your CMI pump rebuild? Did they bring it up to the latest pump configuration for your TSIO-520 called out by CMI? 

Your story is a good lesson/reminder for many that think its okay to load the family up or depart IMC right or even for a long x-ctry flight right after extensive maintenance when really a maintenance flight is is required to prove the aircraft is all okay first. Ground run ups only go so far.

Honestly, I have no idea, these same group of guys have been wrenching for me since I purchased.  Over time, we have found our sources.  But, now that I know there is a "latest pump configuration" I'll be sure to ask.. thank you!!

[EricJ]

I'm glad that came out as well as it did and nothing got bent.    Kudos.

 

[Guest]

I’d be curious to know which adjustment slipped, low unmetered pressure or high metered pressure?  In 35 your of working on TCM engines I’ve never heard of or seen this sort of thing.  Your engine is a plain Jane 340/414 engine if I recall correctly.

General rule of thumb fuel flow should be 9% of rated HP for N/A engines and 11-12% of rated HP for a turbocharged engine.

Clarecne

[Eraaen]

15 hours ago, M20Doc said:

I’d be curious to know which adjustment slipped, low unmetered pressure or high metered pressure?  In 35 your of working on TCM engines I’ve never heard of or seen this sort of thing.  Your engine is a plain Jane 340/414 engine if I recall correctly.

General rule of thumb fuel flow should be 9% of rated HP for N/A engines and 11-12% of rated HP for a turbocharged engine.

Clarecne

From my understanding, it was the high pressure screw.  As described to me, this screw screws out to increase pressure (contrary to my common sense anyway) and then a lock nut tightens in to hold it in place. (I haven't actually seen it) To me it sounds like the "screw" threads must be messed up.  But, the company who rebuilt it says it's a problem with the housing and it's already been sent back.  I am not an expert on Rocket conversions, I just like to go fast.  It is my understanding that these are 340/414 engines that have been detuned to 305HP vs what I think are normally 310HP. It's turbo'd, book says 32-33 gph at full power.

[carusoam]

Great MSer report!

Congrats on making the decision to stay on the ground!

 

I’m in the camp of checking a few things before committing to flight...

• MP
• RPM
• FF
• Each T/O run, as the airspeed comes alive...

These are the signs that the engine is doing its job.  Without these three things, it’s in the ‘I’m not sure enough’ state...

 

Nicely organized and delivered post, Eraaen!

Looking forward to your resolution / follow-ups.

 

Rocket engineering has been pretty good with their STC documentation...

They give complete settings...

But if the settings can’t be maintained... (loose screws)

And the back-up instrumentation can’t be used... (FF instrument)

You don’t have enough reason to continue...

Really tough decision to make while covering over 100’ per second, in flight, watching the runway end approaching...

Nicely done.

Thanks for sharing.

Q: Who to believe?  A: Yourself...  

Best regards,

-a-

 

[Yetti]

I always do RTS flights after maintenance.   If it was alot of maintenance I do fast taxis till I am comfortable.

[Guest]

2 hours ago, Eraaen said:

From my understanding, it was the high pressure screw.  As described to me, this screw screws out to increase pressure (contrary to my common sense anyway) and then a lock nut tightens in to hold it in place. (I haven't actually seen it) To me it sounds like the "screw" threads must be messed up.  But, the company who rebuilt it says it's a problem with the housing and it's already been sent back.  I am not an expert on Rocket conversions, I just like to go fast.  It is my understanding that these are 340/414 engines that have been detuned to 305HP vs what I think are normally 310HP. It's turbo'd, book says 32-33 gph at full power.

This picture of your pump might help.

Clarence

[jaylw314]

21 hours ago, Eraaen said:

I'm not really sure what the moral of this story is.  It should NEVER have left the rebuild company like this.  My guys SHOULD have caught the problem.  I SHOULD have insisted on more follow through/testing before attempting to fly.  Just sharing a story, because it was scary.

Crap!  I'm glad you're okay!  I joke with people that I still can't find my seat cushion after that icing incident, but with that I might have sucked up the entire seat!

[Eraaen]

Clarence.  I was just looking at this schematic yesterday with the guys at the shop.  So, what happened is, the Aneroid Adjustment as it is pictured, controls the high pressure.  The locking nut doesn't actually thread onto the screw as I imagined.  It threads into the housing.  In my case, the replacement housing threads were jacked.  It felt like it tightened, but wasn't going in far enough.  It was loose enough that the adjustment screw could still be turned by hand.  That's the issue that wasn't caught the first time.

[carusoam]

That sure is a complex pump, with its control system...

I’m glad you guys can share these details so well.

Best regards,

-a-

[Guest]

8 hours ago, Eraaen said:

Clarence.  I was just looking at this schematic yesterday with the guys at the shop.  So, what happened is, the Aneroid Adjustment as it is pictured, controls the high pressure.  The locking nut doesn't actually thread onto the screw as I imagined.  It threads into the housing.  In my case, the replacement housing threads were jacked.  It felt like it tightened, but wasn't going in far enough.  It was loose enough that the adjustment screw could still be turned by hand.  That's the issue that wasn't caught the first time.

Over the years I’ve adjusted many TCM fuel systems.  The thread on the aneroid adjustment screw is very fine and doesn’t take a lot of torque to secure it.  I’ve never seen a pump as you’re describing it, all that I have seen have a female thread in the aneroid housing and and external check nut on the adjustment screw.

If you’re able to get it a picture would be helpful.

Clarence

[320KPH]

Awesome result from the aborted takeoff... must have been sporty!

[aviatoreb]

Wow!

Good recovery sir!

[HRM]

On 6/21/2018 at 11:59 AM, Yetti said:

I always do RTS flights after maintenance.   If it was alot of maintenance I do fast taxis till I am comfortable.

Ditto.