R-985 Mech fuel pump failure.

[Dog]

Anybody know of one failing? And if so why?

[Beaver Driver]

Yes I've had them fail.

I was flying a Weatherly 620B sprayplane. I was getting loaded for my 4th or 5th load of the day, and I notice my loader looking at something under the engine. He comes back and tells me there is fuel pissing out the bottom of the airplane. I shut down and call maintenance to see if I can at least fly off this load (I already knew the answer, but you gota keep the boss happy). The thing was that one of the other pilots had noticed it right after I started up that morning, but just figured I had overprimed it, so he didn't say anything.

Obviously the pump had not failed completly, but it could have at anytime. I think the engineer told me the diaphrams get old and start leaking.

I have heard of guys flying home in a Beaver using the hand pump to keep the engine running.

[Dog]

I had only heard second hand of them going. I had one stop pumping gas the other day. The plane I was flying has electric boost pumps that gave the engine back the happy sound right away.
The pump had 50hrs soh. The funny part was I was doing line indoc and the check pilot had just dosed off. Not a nice way to wake up.

[swede]

Just giver on the ole wobbly pump, not a problem..

[twotter]

Hey buddy.. yup, had one go on me last fall... First one I ever heard of happen without warning.. I was just on the slide out of Egmont and the light came on.. My first thought was that I'd done something wrong.. finger trouble.. So I wobbled it and did a little troubleshooting while on the slide and once I was airborne kinda figured that yes, I had gas, yes I was on the right tank etc.. Well you know the routine.. First one for me in over 25 years.. They usually just get weak and you will notice at idle that they won't keep the px up.. this one just quit and did not come back..

ps.. the company that had overhauled it 76hrs previously has since fired the guy who did it...

[dash2/3]

ever heard of "over wobbling" to the point of engine failure induced by this?

[swede]

You can't "overwobble", as far as the other guy saying he had an eng. driven pump fail on the slide, not sure why you would continue the take-off with a fp lite on, unless to get back to a reasonably close maint. base. It would be a little difficult to fly, wobble, raise flaps, run the power, etc.,etc. at the same time..

[twotter]

It was busy, but doable.. Sometimes it makes more sense to continue than abort for a minor problem like that..

[Hey___Pilot]

Hello

[Cat Driver]

I Have only had one engine driven fuel pump fail on P&W's in the last forty years of flying them. I have well over ten thousand hours on Pratt radials.

But I've had two PT6's quit because of fuel controllers.

Cat

[Dog]

I guess the fuel controllers are problematic. Every single engine pt-6 machine I've been in has the manual power lever. That only helps you out if she spools down to sub-idle though.

[chubbee]

a failed drive coupling to th PT6 FCU will produce the opposite. The fuel flow goes to max when the plastic breaks and the engine goes to "war emergency" power right now. Could be interesting on a twin.

[swede]

Yeah and the problem with that is, if you don't confirm with the gauges which side the failure is on, you are going to shut down the good engine. Either way, there is going to be some major yaw action when you go from something like 120% or more of max tq to zero.

[philipturland]

our stbd pump failed on our 18

dry seals which then broke down and caused it to leak

http://beechrestorations.wordpress.com/ ... gust-2012/

The Insignificant “s”

Whilst somewhat intriguing this is exactly what it seems – the misreading of a small word could lead to a no start on an engine.

This may not normally be a problem – pilots tend to try one engine and if it does not fire they try the other one. In doing this the pilot of a Beech 18 3N, 3NM or 3TM series

Since starting the Port engine for the first time in May of 2011 the starboard engine has been the focus of our attention.

Up to now all attempts at starting this engine failed—the starter turned the engine over but she failed to catch.

Initially it seemed that fuel was getting to the top cylinders through the priming system but fuel failed to atomize into the cylinders through the carburetor.

The propeller oil leak which was explained in a previous newsletter was cured after fitting a new seal—we were now into diagnosis and fault finding.

There was a school of thought that the starboard carburetor was causing the problem. You may remember we had a similar issue with our Port carburetor.

We had been offered a carb by Andy Foan who operates the Exeter Beech 18 and we had been given a few pointers as to what may possibly be the problem.

Thinking logically it seemed pointless to strip out a carb, fit a new one and potentially be left with exactly the same fault at the end of 4 days of work only to have to repeat the whole process in reverse if it didn’t cure the problem.

A quick check of the fuel system in the Expeditor 3 manual indicated that there was a fuel check valve in the circuit.

The Check valve allows fuel to flow from the tank to the pumps, carbs etc. It is one way and prevents fuel flowing back to the tank—the first thing was to check this as it is easy only consisting of 1 connection from the bulkhead to the fuel pump.

This was disconnected and the system pressurized on the wobble pump—pressure was felt at the pipe end thus testing the correct functioning of the check valve.

Next in line is the fuel pump—fuel was seen to be leaking during attempts to start—the fuel pump seemed to be leaking out of the overflow which discharges to air.

The pump was removed for investigation. Upon disassembly the internal seal was found to be damaged rendering the pump un serviceable.

We did not have a spare pump to hand. A new pump was sourced and fitted the following weekend and again pressure tested—this time the pump did not leak, fuel pressure was maintained indicating to us the fault had been cured.

On the 30th June we prepared for an engine start— we pre-oiled, pulled through and we were ready to try.

Select engine to start, select fuel tank, wobble pump to build fuel pressure, prime 7 strokes engage starter and ignition booster, let it turn 7 blades, switch on magneto—it should fire but it didn’t.

Were back to square one with a possible carb problem.

One of the suggested problems for which we thank both Andy Foan and Rex Ford is an ignition issue. To test this we removed all 9 front spark plugs to check for an ignition source “a shower of sparks”. This shower of sparks is produced by the induction vibrator box located on the engine bulkhead.

We had a spare which Dave examined to understand its operation. He realized that this provided a shower of sparks to the rear set of plugs! I was now into re-installing all of the front plugs and removing rear plugs to establish if we had the correct “shower of sparks” – We did—so we had fuel pressure, a new fuel pump an ignition source what could it be.?

I decided to check one last thing—priming. I disconnected the line at one of the cylinders and got Dave to prump the primer—nothing but air came out—NO FUEL.

We now consulted the Expeditor 3 fuel system circuit diagram. This is when it all became clear. Checking the diagram we could now see that the engine priming system gets its fuel from the left (Port) engine fuel strainer.

What does this mean?

It means that unless you have either the left engine running or at the very least a left fuel tank selected it is impossible to prime the right or Starboard engine!

We selected a port tank – selected right engine on the primer – pumped it and fuel came out. Not just a dribble but a good gout of it.

I re-connected the primer line—pushed the Beech out of the Hangar (well not on my own), went through the starting procedure described earlier and guess what—she literally roared into life and ran very sweetly indeed. We then decided to start the Port engine—History was now being made—history for us anyway as the port engine also came to life.

This was the first time in over thirty years these engines and this aircraft had run on both engines at the same time.

Once we had shut down (this is another issue) we took stock of where we were—I checked the starting procedures for the Expeditor and discovered to my amazement that the procedure in the book was/is very ambiguous and could result in a no start on the starboard engine. It states and I quote “select tanks” select engine to be started—start engine then repeat for port side” – this implies starting of the Starboard engine first which as we discovered is not possible unless you take note of that little insignificant “s” on “select tanks”

[Rowdy]

Have had a couple of weak pumps that were replaced, and one that had failed in flight. Same as twotter, elected to continue home as it would have been a nightmare for mtce anywhere else, plus she wobble pumped just fine. Its even easier when you grab the pax hand, smile and say 'here keep doing this till we land' All jokes aside, use the resources at hand!

[cdnpilot77]

I had one go (dry seals) the day after my first checkout in the amphib beaver and first trip with the boss and his family on board. We were at 5500' and only 15miles from home base and ended with wobbles back home to a safe landing and the boss driving to the cottage.

[shimmydampner]

It was busy, but doable.. Sometimes it makes more sense to continue than abort for a minor problem like that..

Hmm. Seems like fuel pump failure is a perfectly sensible reason to abort.

[iflyforpie]

It was busy, but doable.. Sometimes it makes more sense to continue than abort for a minor problem like that..

Hmm. Seems like fuel pump failure is a perfectly sensible reason to abort.

What's the big deal? He had a working wobble pump. Don't pilots here take off on one mag if the other one fails?

[xsbank]

Hey Pie, no. At least not with passengers. You have no MEL relief.

I have visions of that great Beaver scene in Never Cry Wolf...

[zeppelin]

I had one go on me once half way between McNeil and Campbell,while flying down the straits.I kept going and wobbled all the way to Campbell,with no problem..nothing was said and all pax happy.I remember this because a few months later,I got a call from Transport.One of the pax had reported me for flying an unservisable aircraft.Both Transport and I had a good chuckle,they ended by saying good job on getting it back safely....I wouldn't want that to happen everyday though.

[Colonel Sanders]

One of the pax had reported me for flying an unservisable aircraft

He's actually correct. As soon as the pump failed in flight, for
the remainder of the flight your C of A was no longer valid and
you were illegally flying an aircraft in a passenger-carrying
commercial air service without a valid flight authority.

I've had TC attack me for years for much, much less.