Fuel Pump Failure

[Discap]

I have a friend who balled up his heli after the engine quit with a fuel pump failure. This was a 4 place experimental. The ship was fuel injected and had 2 fuel pumps but at 300 there was obviously no time to restart.

 

So the question is how do certified ship handle a fuel pump failure?

 

Is there a pressure sensor that automatically kicks on the second pump?

 

Thanks

 

Bill

[helonorth]

I think in most piston helicopters, the fuel is gravity fed (at least the ones I flew). In turbines I have flown, there was an engine driven fuel pump along with two boost pumps. I don't think the engine will run with a failure of the engine driven pump, but I have never heard of one. If it did, only one thing to do: autorotation.

 

In your aircraft, they should both be running at all times. A successful air restart of a helicopter is as rare as hens teeth. Trying to restart a helicopter while in autorotation would be more than most pilots could handle and could be very dangerous. Myself, I wouldn't be doing anything but maintaining RPM and looking for a place to land.

Edited November 19, 2018 by helonorth

[Eric Hunt]

Most turbines are able to suck the fuel from the tank with their engine-driven suction pumps if below about 6000'. Above that, the in-tank boost pumps are needed to give positive pressure.

 

Boost pumps are running all the time. In the early B206 they are powered when the circuit breaker is in, even if the battery switch is off. It is possible to leave them running on shutdown and flatten the battery.

[Wally]

Most turbines are able to suck the fuel from the tank with their engine-driven suction pumps if below about 6000'. Above that, the in-tank boost pumps are needed to give positive pressure.

 

Boost pumps are running all the time. In the early B206 they are powered when the circuit breaker is in, even if the battery switch is off. It is possible to leave them running on shutdown and flatten the battery.

 

What Eric Hunt said...

 

One of the reasons some RFMs, some operators want you to run it for a while everyday with the boost pumps off to ensure the supply line is intact. If the line up to the engine is compromised, the boost pumps can deliver enough fuel to keep the engine running but have a leak, suck air sufficient to starve the engine without'em.

 

I believe that injected recip engines must have an engine fuel pump to deliver sufficient flow and pressure for metering...?

 

I think I recall an airframe/engine combination in which boost pumps were only used on starts? Maybe the P&W in the 412?

[Thedude]

GE 701s in Apaches run a boost pump on start up only and have an engine mounted suction pump to supply fuel to the HMU, which is the real fuel pump. Not sure if all applications of the 701/CT7 are similar.

[DizzyD]

The Robinson R44 Raven II has both an engine driven pump and an electrically driven auxiliary pump.

[helonorth]

Well, we went off the rails early with the turbine talk. No relevance. What does the auxiliary pump do in a Robinson? Will it run with just the auxiliary pump.

[helonorth]

 

In the early B206 they are powered when the circuit breaker is in, even if the battery switch is off. It is possible to leave them running on shutdown and flatten the battery.

 

This is true in a all 206's and 407's to this day. But the fuel valve must be left on.

[Flight1]

The R44 has two fuel pumps, one electric (for priming/startup) and runs while the clutch is engaged for redondancy. And a mechanical pump that works while the engine is running. So both pumps are running at the same time, if one fails, the other continues operating, allowing for normal engine operation.

 

There is no emergency procedure for a mechanical (engine driven pump) because it has the auxiliary (electric pump running).

 

AUX FUEL PUMP

Indicates low auxiliary fuel pump pressure. If no other indication of a problem, land as soon as practical. If light is accompanied by erratic engine operation, land immediately.

[Nearly Retired]

Wait... What? This thread brings up SO MANY QUESTIONS!

 

1) A four-place experimental with a fuel-injected piston engine? Soooo, maybe I've been out of aviation for too long (you know, like Avbug), but what ship is this? Only one that I think might qualify is the Hummingbird (depending on which engine is installed).

 

2) Balled it up because he couldn't do an auto from 300 feet? Hmm, you know, maybe we shouldn't be flying around at 300 feet! Just sayin'.

 

3) FAA Standard Category Certified helicopters usually do not have "backup" or "standby" fuel pumps that kick in automatically if the primary fails. We don't have that sort of witchcraft technology in helicopters! As has been pointed out, some ships with carburetors use a very simple gravity-feed system with no fuel pump at all! Fuel-injected engines need positive fuel pressure at all times so they'll have some combination of engine-driven and electric boost pumps. If a fuel pump fails and causes the engine to quit, there probably won't be any restarting. Why? Because most of us fly too damn low all the time (see #2 above).

 

And finally...

 

4) The Bell 206: (And this is waaaaay off-topic.)

 

a. It is only in the Bell 206L-series (and 407) that *one* of the boost pumps is wired directly to the battery buss. But the power wire goes through the fuel valve switch. So if you were to inadvertently leave the left fuel boost switch (circuit breaker, actually) on *and* accidentally leave your fuel valve on...well...you're a pretty bad pilot. And you'd quickly have a battery that's as dead as Elizabeth Warren's career as spokesperson for the Cherokee Indian Nation.

 

b. Model 206B-models do not have this feature. You can leave the fuel valve on all the time for all I care. I mean, really, I don't care. DO IT! (Except that the RFM tells you not to.)

 

c. The engine-driven fuel pump in a 206 (RR 250-series engine, actually) is what they call a "positive displacement pump." What that means is that when the pump is not turning, no fuel goes through it no matter how hard those little booster pumps in the fuel tank are squeezing it into the lines. And yeah, I do know of a case in which an engine-driven pump failed in flight. Friend of mine was on a photo shoot at about 300' when it happened. Crashed that bitch but good!

 

Ain't aviation fascinating?

[iChris]

So the question is how do certified ship handle a fuel pump failure?

 

Thanks

 

Wait... What? This thread brings up SO MANY QUESTIONS!

 

c. The engine-driven fuel pump in a 206 (RR 250-series engine, actually) is what they call a "positive displacement pump." What that means is that when the pump is not turning, no fuel goes through it no matter how hard those little booster pumps in the fuel tank are squeezing it into the lines. And yeah, I do know of a case in which an engine-driven pump failed in flight. Friend of mine was on a photo shoot at about 300' when it happened. Crashed that bitch but good!

 

Ain't aviation fascinating?

 

Some are unaware of that fact, with respect to the turbine helicopter, failure of the mechanical (engine driven) fuel pump will result in engine failure. The boost pump will not prevent the failure. Boost pumps can’t provide the required pressure nor volume to the fuel control unit for turbine operation. Boost pumps are mainly there to provide positive fuel pressure in the fuel line to the engine driven fuel pump inlet, thereby preventing cavitation (air) in the line.

 

Consequently, turbine engine helicopters most often have a dual element mechanical fuel pump consisting of two parallel pump elements. Either element capable of supplying enough fuel to meet all engine requirements. That’s notwithstanding catastrophic single point failures like the Bell 206 accident listed below:

 

With regard to post #1 - As far as that fuel pump failure in the 4-place piston experimental, it had two fuel pumps. Whether it was capable of operating on either pump cannot really be determined, not enough information on either pump or their capabilities and limitations. Being it was an experimental, the individual’s technical expertise and experience in maintenance and assembly also comes into question. They say it’s possible on some piston helicopters, like the R-44 II, under that same circumstance, to function normally with either the engine-driven or auxiliary pump as the sole pump:

 

“R44 II fuel system is a pressurized fuel system that includes an engine-driven pump, an auxiliary (electric) fuel pump, and a fuel return line which allows pump supply in excess of engine demand to return to the fuel tanks.”

 

“The R44 II auxiliary pump primes the engine for starting and runs in flight to provide fuel pump redundancy. The engine will function normally with either the engine-driven or auxiliary (electric) pump operating. The ignition switch prime (momentary) position operates the auxiliary fuel pump for priming prior to engine start. After start, the pump runs continuously as long as the engine has oil pressure and the clutch switch is in the engage position.”

 

“Proper mechanical fuel pump function is indicated by normal engine operation after engine start prior to clutch switch engagement and before shutdown while clutch switch is disengaged.” Ref, R-44 Maintenance Manual

 

"An inflight loss of engine power due to a failure of the engine fuel pump, which resulted in a collision with trees and terrain during the subsequent autorotation. The failure of the engine fuel pump resulted from the absence of adequate grease leading to accelerated spline wear within the fuel pump."

 

“Following an inflight loss of engine power, an autorotative landing can be accomplished if the pilot successfully enters the autorotation, the helicopter has adequate altitude and airspeed, and rotor rpm is managed throughout the autorotative descent. The lack of crash-resistant data and cockpit image recorders, radar data, or surveillance videos precluded determination as to why the pilot was not able to successfully complete an autorotation.”

CLICK PHOTOS TO ENLARGE

 

 

Pigeon Forge, TN, Bell 206, Loss of engine power (total) Part 91: General Aviation - Aerial Observation - Sightseeing, 5 Fatal

Edited November 22, 2018 by iChris

[Discap]

Sorry about disappearing like that, been traveling for the holidays. Yes the ship was a Hummingbird. The owner had difficulty with the auto because of the terrain and trees, actually did an amazing job.

 

The ship is equipped with two fuel pumps, either of which is more than enough to run the engine. He was running with only one on, per the POH. It seems to me that running with only one is a bad idea.

 

If however you always have two pumps turned on, then how do you know if they are both working. I could envision a check valve after each pump with a pressure transducer on each one going to an indicator. Is this what Robinson does.

 

Bill

[iChris]

The ship is equipped with two fuel pumps, either of which is more than enough to run the engine. He was running with only one on, per the POH. It seems to me that running with only one is a bad idea.

 

If however you always have two pumps turned on, then how do you know if they are both working.

 

I could envision a check valve after each pump with a pressure transducer on each one going to an indicator. Is this what Robinson does.

 

Robinson (R-44 II) does it off a pressure switch and cockpit light as given below:

Verification of proper operation of the auxiliary (electric) pump is accomplished with actions [a] and resulting as follows:

 

[a] Aux fuel pump caution light - OFF

 

and

 

Aux fuel pump caution light - ON

 

Verification of proper operation of the mechanical fuel pump is accomplished with action [c] resulting as follows:

 

[c] Normal engine operation with the and the Aux fuel pump caution light - ON

 

 

[a] The ignition switch prime (momentary) position operates the auxiliary fuel pump for priming prior to engine start. After start, the pump runs continuously as long as the engine has oil pressure and the clutch switch is in the engage position.

 

A pressure switch downstream of the auxiliary fuel pump illuminates the aux fuel pump caution light if auxiliary pump output pressure is low. When the clutch switch is disengaged, the auxiliary pump is off and the aux fuel pump caution light should be illuminated.

 

[c] Proper mechanical fuel pump function is indicated by normal engine operation after engine start prior to clutch switch engagement and before shutdown while clutch switch is disengaged.

CLICK PHOTOS TO ENLARGE

 

Edited November 23, 2018 by iChris

[iChris]

The ship is equipped with two fuel pumps, either of which is more than enough to run the engine.

 

He was running with only one on, per the POH. It seems to me that running with only one is a bad idea.

 

It depends on the manufacturer/model, MD500 D/E, MD600N, MD520N, use the Start Pump (aka boost pump) as desired and limited to malfunction procedures and preflight checks as described for the airframe fuel filter installation. On the MD530F Plus, the Start Pump is now optional equipment.

 

Most Bell helicopters document all boost pumps ON in flight.

 

Sometimes it maybe an engine thing, the Pratt & Whitney PT6T-3/6 (Currently used by BH-212, BH-412, and SK-58T) penalize boost pumps OFF operation in their maintenance manual with a limitation that could require removal and replacement of the engine driven fuel pump.

CLICK PHOTOS TO ENLARGE

 

If however you always have two pumps turned on, then how do you know if they are both working. I could envision a check valve after each pump with a pressure transducer on each one going to an indicator. Is this what Robinson does.

 

Experimental pilots often overlook Service Bulletins in their quest for the cheapest price on new and used parts, especially engines. Some of those accessories may have a maintenance/recall issue. So what was the true history and airworthiness status of that Fuel Pump. Lycoming has a number Service Bulletins out on Fuel Pumps, 590A, 599 621B, and 548A to name a few.

 

Edited November 23, 2018 by iChris

[Nearly Retired]

Ah, for want of a $65 fuel pump a helicopter was lost...

 

Discap, you said:

 

The owner had difficulty with the auto because the of the terrain and trees, actually did an amazing job.

 

Not an "amazing job." The Hummingbird pilot “got lucky” is all, in that he was flying solo and he was over a sparsely populated area of upper New York State. Had either of those conditions not been met, the outcome of his auto-to-the-trees might have been tragically different. See, by Federal Aviation Regulation (91.13) we are legally not allowed to endanger anyone (in the air or on the ground), nor are we allowed to endanger anyone's property either. That sort of obligates us to always maintain an altitude and a flight path that ensures we always have good forced-landing areas underneath us.

 

Of course, “danger” is a nebulous term, and it's often hard to prove. However, the FAA likes to hit you with a violation of the “catch-all” 91.13. Especially if you say, “I was too low to do a successful auto.” Again, he was lucky no one got hurt and he didn't damage anything on the ground except some trees (and his own helicopter).

 

But man, in that part of New York State there really aren't that many “good” forced-landing areas! If you Google Map the route from his departure point (Potsdam Airport) to his house...I mean, jeez...it's pretty heavily wooded. Especially that last eight miles or so. That area south of Rt. 58 is ugly. In a single-engine helicopter you'd have to pick your route very carefully or go waaaay high to always keep a good forced-landing area within reach. Honestly, I don't know which I would've chosen. (Spoiler alert: I probably would've crashed too.)

 

Now let's look at the helicopter. The Hummingbird is basically a Sikorsky S-52 with a JetRanger-like nose. It was marketed for a while as a “kitplane” by the wonderful Clark family at Vertical Aviation Technology. As the military HO5S-1 it originally had a six-cylinder Franklin in it. VAT tried a number of different engines. N4045 had the Chevy LS3 V-8. It is fuel-injected and, in this installation uses two $65.00 Airtex automotive electric boost pumps to deliver fuel from the tank to the engine. They're not very heavy-duty.

 

Trouble is, the designer only called for one pump to be operational in flight, which should have been sufficient. But as you note, there was no automatic switch-over of any kind should one pump fail. The only way you know the first Airtex pump has failed is -bloop! - when the engine quits. And because we helicopter pilots usually fly so low, there's often no time for troubleshooting and restarting. I know, I know...there are procedures for such a thing. It's pure fantasy. The reality is, you just go to the ground.

 

The Chevy's fuel injection system was evidently not strong enough to suck fuel up from the tank. I'm not familiar with how Chevy does it, but I imagine that the F.I. has an internal pump to squirt fuel through the injectors. Like most cars, it needs a “boost” pump running all the time to supply positive fuel pressure, which eliminates the old diaphragm-type fuel pump that used to be mounted on the side of the engine. In cars, electric pumps do fail! I've changed a number of in-tank fuel pumps over the years.

 

In the case of the Hummingbird, a better procedure would've been to just leave both pumps running in flight for some redundancy - especially during takeoff and landing and flight over rough/unsuitable terrain. Because even some sort of automatic switch might not have kept the engine from quitting unless the system was designed to detect even a small drop in pressure from the first pump. If the second one didn't kick-in until the first one was completely off-line...well...that engine would probably already be dead from fuel starvation.

 

Hey, live and learn...

 

I used to fly old Sikorsky's myself. The S-55/H-19 normally uses a very stout aviation-type electric fuel boost pump that is only used for starting. They're ancient and they fail. So in most of the ships, the operator replaced the old pump with an external, in-line pump. But it is a huge, aviation-type pump (don't ask me who manufactures it though). Luckily, the radial engine has an engine-driven fuel pump that can suck like one of Michael Avenatti's clients. "Golf ball through a garden hose" is the expression that comes to mind.

 

So...a couple of lessons from this accident. 1) There are usually pretty good reasons that automotive parts should not be used in aircraft. 2) When flying a single-engine helicopter, always always always fly with a good forced-landing area within reach. Vary your altitude and/or route to make it so.

Edited November 23, 2018 by Nearly Retired

[500F]

 

 

It depends on the manufacturer/model, MD500 D/E, MD600N, MD520N, use the Start Pump (aka boost pump) as desired and limited to malfunction procedures and preflight checks as described for the airframe fuel filter installation. On the MD530F Plus, the Start Pump is now optional equipment.

 

Most Bell helicopters document all boost pumps ON in flight.

 

Sometimes it maybe an engine thing, the Pratt & Whitney PT6T-3/6 (Currently used by BH-212, BH-412, and SK-58T) penalize boost pumps OFF operation in their maintenance manual with a limitation that could require removal and replacement of the engine driven fuel pump.

CLICK PHOTOS TO ENLARGE

 

 

Experimental pilots often overlook Service Bulletins in their quest for the cheapest price on new and used parts, especially engines. Some of those accessories may have a maintenance/recall issue. So what was the true history and airworthiness status of that Fuel Pump. Lycoming has a number Service Bulletins out on Fuel Pumps, 590A, 599 621B, and 548A to name a few.

 

 

 

The electrical fuel pump has always been optional in the 530F. I'm not sure if the FF was different.They actually call it a maintenance pump, because the only time you need to run it is to de-fuel the aircraft. I flew a 1984 530F the other day. Still no electric pump in it.