Baron boost pump life with continuous use? safe to fly?

[Bounceferret]

Had an interesting one a few weeks back near northern SA

Noticed the RH fuel pressure fuel pressure gauge 'flickering' slightly, kept an eye on it and continued to our destination which was aprrox 1 hour away.
15 mins later the flicker progressively got worse and pressure seemed to be dropping slightly, prompting an increase in RH mixture to return to normal PSI. This continued happening over the next 5-10 mins or so until the needles were fairly split with near full mixture.

Few mins prior to this I opted to climb from a relatively low 500' to 9500' with the boost pump on low. Top of climb, turned pump off, and not too surprisingly the RH engine lost almost all power, switched back on to low, power regained. At this point I guessed EDP failure and continued to our landing point....
Turns out it was something unrelated causing fuel starvation.

As the plane was hired I contacted the owner and advised of the situation and our fairly remote location.
During ground runs discovered the engine was developing full power with pump off but needles split approx 4-6 psi...
End of story we flew back home with the boost pump on low and used hi for take off in order to get 16+ PSI req'd for t/o

My question, how long do beech boost pumps last for with continuous use? and how safe is it to fly on one if the EDP had indeed failed?
As I believe they are not an immersion pump (which last for ever) and instead run in 'series' behind the EDP (remember at this time I assumed the EDP failed and was mindful of the possibility the delivery line could become blocked with a damaged pump components)

oh, and minimise the flamming about what could/should/would have happened

Cheers,

[chimbu warrior]

Been a while since I flew a Baron, but most Continentals are similar.

It is, as you have stated a boost pump, and my understanding is that they are designed to supplement, rather than replace, the EDP. I'd therefore tend to agree with you that prolonged operation of the pump is unwise, and probably not recommended by the manufacturer.

A Baron POH may offer some suggestions or clues.

[Ex FSO GRIFFO]

Dives into dusty ole drawer and finds BE-58 POH - 1972 series......

"Aux Fuel Pumps;
An individual two-speed electric aux fuel boost pump is provided for each engine.HIGH press. OFF, or LOW press is selected with each aux fuel pump switch on the pilot's sub-panel.
HIGH press is used for stablizing the fuel press before starting and provides near max engine performance should the engine-driven pump fail.
In high ambient temps, LOW press should be used for ground ops, take-off, and climb.
The location of the aux fuel pumps in the system permits fuel to be drawn from any cell within the system by the pump for the operating engine.
The HIGH position should not be selected while the engine is operating except in the event of engine driven pump failure since the HIGH press mode supplies a greater pressure than can be accepted by the injector system for a reduced power condition."

That's all it says folks.
Page 6-17 in my Beech POH.

The Emergency Procs for crossfeed talk about Aux fuel pump - LOW or OFF as req'd.
Page 3-8

Doesn't really answer yr query I know, but that is all the 'good book' says.....

Re your 'turns out something unrelated' comment....care to elaborate?
Not wishing to guess anything 'evil'....just curious is all.....

Cheers:p

[lemel]

As Ex FSO GRIFFO quoted, it can be used in the event that the engine driven fuel pump fails.

As far as I was concerned when I was flying the beast was that the aux pumps can be operated for a prolonged period of time in the above sitation without any issue.

But remember they are a backup for the engine driven pump and as such I wouldnt be inclined to fly multiple sectors with only the aux pump(s). If the engine driven fuel pump failed inflight I would return to departure aerodrome, divert or continue to the destination as I saw fit and once I landed I wouldn't be taking off again.:=

[patienceboy]

I would treat any abnormal situation (especially fuel related) as highly suspect and act as if the worst case were to transpire. What if the electric pump fails as you rotate? What if you have an electrical smoke/fire event and have to turn all the electrics off? In any case the aircraft is legally un-airworthy.

[Bounceferret]

Ex FSO GRIFFO

Turned out a pest had made a nest in upper regions of the main tank vent, not allowing pressure inside/outside the tank to equalise and very difficult to discover during a daily. The EDP didn't have enough power to deliver fuel alone after 1+ hour flight....... my thoughts now lie with what happened to the bladder inside the tank?? probably got a bit smaller :ooh:

patienceboy

The thought of rotate failure or efato did pester me for a while.
But had flown this a/c several times before, knowning it will +roc on 1 engine for a modest DA, we weren't mtow, had no take-off clearance issues and it was the RH engine..... and most of all the engine was still developing full power with the aux pump off, albiet at a lower pressure (the IO470 req's a min 20g/ph at t/o setting to remain "happy and cool"... which we would have been a little under if the aux pump failed but still would have had both engines one with a higher CHT)

[Ex FSO GRIFFO]

Thanks for that.

Cheers:ok::ok:

[patienceboy]

So the boost pump was only masking the problem (incorrectly assumed to be the engine driven pump) for an unknown period of time. The engine probably would have failed again once the pressure of the two pumps combined wasn’t enough. That’s what I mean by treating any abnormal situation as suspect. Always play it safe if there is any doubt - especially if you have passengers.

Disclaimer: My answer is aimed at your questioning whether it is safe and is general in nature. I don’t know much about the baron specifically! .:ok:

[QFF]

If I suspected an engine driven pump failure, I would be headed for the NEAREST suitable landing site.

Sure the electric pump would keep the fuel pressure up, but if the engine pump was failing, who knows whether/when it would disintegrate, shedding bits into the engine and causing a premature and uncommanded silence up front...

(Now if I was in the middle of the Nullabor, that's another matter...:})

[Bounceferret]

Over Lake Eyre... not far off :suspect:, and our destination was the nearest suitable.
Though this wasn't a failed engine, and didn't necesitate urgency actions or a call to centre... though they were informed.

If the engine couldn't develop full and consistent power during ground runs without use of the boost pump the decision would have been simple.