mburch

mburch

Well Known Member
Patron
...was the headline that grabbed my attention in the latest issue of the RV Builder's Hotline. Click here for the NTSB report.

Now I'm all nervous, since I had to replace my fuel pump after I got stupid and cracked the casting while screwing in the vent fitting. I knew from the overhaul manual that it can be tricky to get the new pump installed, but it didn't seem to give me much trouble at the time... I just rotated the crank until the pushrod could be raised up, then sort of finagled the pump into place. It didn't really give me any resistance or anything. Honestly the hardest part was getting the safety wire just right.

Should I be worried? How obvious is a mis-installed fuel pump? :confused:

mcb
 
Engine difficult to restart?

The following line in the NTSB report got my attention. Can someone explain what the recommended method of restart is in this situation? Are the odds of restarting a starved carbed engine any better?

"Pilot's Handbook of Aeronautical Knowledge states that, in regard to fuel-injected engines, it is difficult to restart a hot engine or an engine that quits because of fuel starvation"
 
Should not be an issue...

flybye said:
The following line in the NTSB report got my attention. Can someone explain what the recommended method of restart is in this situation? Are the odds of restarting a starved carbed engine any better?

"Pilot's Handbook of Aeronautical Knowledge states that, in regard to fuel-injected engines, it is difficult to restart a hot engine or an engine that quits because of fuel starvation"
Click to expand...

I have purposely starved my engine in flight. Restart was immediate when fuel flow was re-established. I will let the experts respond to proceedure, but mine would simply be Mixture in, Boost Pump on.
In a Hot Start under this scenerio, fuel has not had time to vaporize and it is not even in the lines to do so if it has been starved. From 5000 ft, the prop should be windmilling well beyond what a starter could do, so restart should be a non issue if there is fuel. I dont understand the NSTB's response in regard to starting being difficult considering the circumstances here.
 
Restart

An inflight restart is not the same as a hot start on the ground. The airflow will not allow the heat soaking that causes problems in injected engines. The windmilling RPM will deliver fuel to the injector (or carburetor) fairly quickly. The NTSB seems to use some canned phrases in reports that don't quite fit the issue at hand.

John Clark
RV8 N18U "Sunshine"
KSBA
 
mburch said:
...was the headline that grabbed my attention in the latest issue of the RV Builder's Hotline. Click here for the NTSB report.

Now I'm all nervous, since I had to replace my fuel pump after I got stupid and cracked the casting while screwing in the vent fitting. I knew from the overhaul manual that it can be tricky to get the new pump installed, but it didn't seem to give me much trouble at the time... I just rotated the crank until the pushrod could be raised up, then sort of finagled the pump into place. It didn't really give me any resistance or anything. Honestly the hardest part was getting the safety wire just right.

Should I be worried? How obvious is a mis-installed fuel pump? :confused:

mcb
Click to expand...

Matt,
If it went in easy you should be fine, sounds like you did it right. If you don't get the arm up (it usually falls down when you take your finger off it) and then you force the pump on with the bolts you have problems. As long as the bolts went in evenly and easily you should be fine. You should also have good fuel pressure at idle also. I like to crank it around by hand afterward with the plugs out to feel it sucking and blowing which it will do even at that speed and you can also check for smooth operation. Can't say I have ever heard or felt one installed incorrectly but I would think there would be some unusal resistance/vibration or some kind noise coming from the pump when spinning by hand.
 
I little more info please!

I will just be starting my fuselage next month, so I am definitely not ready for the fuel pump yet.

Help me out here, in the injected RV's isn't there a backup electric pump in the system also?

There sure is on certified injected setups.

Do some people skip the electric backup?:confused:

If that is the case you might save some $$ but lose your a$$ doing it.:eek:

It is a sobering thought to come out of the sky, a deadly lesson in the reliability of gravity verses the reliability of machines, however well constructed.

I feel for the family.:(
 
Boost pump?

What about the electric fuel pump? One of its purposes is to serve as a back up for the mechanical fuel pump. Loss of the mechanical fuel pump shouldn't necessairly result in engine failure.
 
I am also worried about this. I removed the mechanical fuel pump off my engine in order to install the fuel overflow part from Vans. My engine was already mounted and I could not put the part in due to interferences with the RV4 firewall. I am definitely going to do more research on this.
 
No

GAHco said:
I will just be starting my fuselage next month, so I am definitely not ready for the fuel pump yet.

Help me out here, in the injected RV's isn't there a backup electric pump in the system also?

There sure is on certified injected setups.

Do some people skip the electric backup?:confused:

If that is the case you might save some $$ but lose your a$$ doing it.:eek:

It is a sobering thought to come out of the sky, a deadly lesson in the reliability of gravity verses the reliability of machines, however well constructed.

I feel for the family.:(
Click to expand...

Nobody leaves out the backup electric pump. Some of us leave out the mechanical pump and go with dual electric (and boy I have yet to find a single good reason for using a mechanical pump..OK resistance to lightning stikes not withstanding).

Sounds like the pilot simply forgot to flip on the electric pump.

I would also suggest an audible fuel pressure alarm from the Dynon draws your attention to the issue.

Frank
 
I like the mechanical pump because:

1. it's independant of the system that backs it up
2. I've only seen one failure in 5 years as a professional mechanic, many many more electric failures.
3. They last forever (years wise, our cardinal's is 35+ years old, no issues, same with the canister type boost pump though. Can't be said for the little box-type pump Van's recommends.)
 
The report says that the electric boost pump switch was found in the ON position. This does not tell us when it was placed in the ON position or how much time had elapsed from the initial failure. Bench testing revealed the pump provided pressure when "held in the ON position." Was the switch damaged in the accident sequence? Faulty contact in the switch maybe?
 
BOOST PUMP SWITCH

I was told recently by someone form N. Calif that the boost pump switch was a circuit breaker/switch combination and there was an issue with the switch. This is in line with the investigators statement that the boost pump would run with the switch held in the on position.
 
Restarts aren't straight forward

I know from experience of flying a jump plane (cherokee six IO540 engine) that restarts aren't always successful. We had a fuel vent problem with one tank that wasn't found as it occurred rarely over a period of a year or so. When the engine quit on me I managed to restart it by closing the throttle fuel pump on changing tanks and then opening the throttle again. It worked, however on two other pilots when the same thing happened they ended up in fields. After the third failure over a 12 month period they stripped the whole system and finally found a blockage in one of the tank vents.

I know when flying twins if you do an engine shut down in flight they can be hard to restart. It doesn't take long for them to become cold soaked.

Peter
 
If one of check valves fails in the fuel pump and gets stuck closed, it would be impossible to pump fuel thru it via the electric pump.
 
Valid points

osxuser said:
I like the mechanical pump because:

1. it's independant of the system that backs it up..Very true

2. I've only seen one failure in 5 years as a professional mechanic, many many more electric failures....But how many vapour lock issues running mogas in a low wing airplane?..There are others on this list who would suggest they do fail.

3. They last forever (years wise, our cardinal's is 35+ years old, no issues, same with the canister type boost pump though. Can't be said for the little box-type pump Van's recommends.)

Cardinal is a high wing which is much less likely to VL than a low wing especially running mogas on a hot day. Not saying your wrong..Each to their own comfort level but the mechanical pump does have the serious drawback in that it is in the worse possible place hydraulically speaking.
Click to expand...

And now I have to add words to make it long enough..:)

Frank
 
You must log in or register to reply here.