Engine Hours

[paul330]

Couple of quick questions about engine paperwork -

- Are engine hours counted from the Hobbs, block time or flight time?

- All the advice and paperwork for fuel flow checks prior to permit issue mention carburetors. Is the check required for injected engines?

[Kevin Dilks]

Hobbs hours so long as it only registers when engine running as opposed to switching the power on ...............................

Kevin

[AlanR]

Very much a moot point, but all Aircraft Log books are supposed to record flight time....

[Steve Brown]

Engine and airframe log book hours are take off to touch down - anything else 'ages' your engine prematurely by perhaps 20%; pilot log book time is brakes off to brakes on.

'Hobbs' time can be misleading - much depends on how they have been installed some run once the master switch is on, others once either any rpm or above a set rpm or oil pressure is detected, others on an undercarriage squat switch.... etc.

No reason for FI fuel flow checks to be any different to a carb thus fuel flow to throttle/injector body should exceed the published requirements.

Regards
Steve

[paul330]

Thanks for the replies.

So, engine and airframe hours are flight time. My Hobbs will work off oil pressure so not accurate in this case. Guess you have to remember T/O - Ldg times. Or I'm pretty sure the Skyview will have something that can track it.

My build inspection schedule lists fuel flow check. It's just that all the forms seem to refer to carbs. As I understand it, the full power engine check is NOT required and it is sufficient to check the electric fuel pump.

[mike newall]

If you work on tacho minus 15% it is about right.

I have done that for 30 years........

Tacho time reads at cruise rpm. The 15% reduction allows for the other bits.

This was advice given by good Engineers at Yorkshire Light Aircraft.

M

[mike newall]

Further to last.

You only have to prove the electric pump delivers sufficient flow - do not, I repeat, do not start messing around with fuel flows with engines running.

Far too dangerous

[Ian Melville]

Further to last.

You only have to prove the electric pump delivers sufficient flow - do not, I repeat, do not start messing around with fuel flows with engines running.

Far too dangerous

Rotax 912 has a mechanical pump, you need the engine running for that? The process was described to me once, and it did sound a bit risky

[AlanR]

I think the LAA requirement is still the same as it was a couple of years ago. That is that a full engine rev check of fuel flow via the mechanical pump is required on initial permit of an aircraft.
As said, it is rather nerve racking standing alongside an aircraft with a fuel tube going into a measuring jug whilst the aircraft is at full revs.

[Steve Brown]

Hi again
Have a look at this

http://www.lightaircraftassociation.co. ... ystems.pdf

Note that it is often impossible to get full power on the ground with a fixed pitch prop. My O-200 max static is 2400 rpm (65% power) vs 2750 rpm (max power) so a ground run is bit meaningless in that respect really.

Also note in TL 2.20 that LAA sensibly and specifically acknowledge the safety / danger (props, fire & aircraft runaway) aspects of running engines at 'full' power and simultaneously trying to control fuel pressures and measure flow rates.

quote

Safety is paramount and, for aircraft with larger, more powerful engines, carrying out this procedure may be considered to be unacceptably hazardous. LAA, therefore, does not consider that a fuel flow check of the mechanical fuel pump is mandatory.

If the engine manufacturer quotes the fuel flow rate at max power this could be used to assess effectiveness of the electric fuel pump (taking care to ensure the fuel system configuration is taken into account). That is, if the electric pump can only feed the engine through the non-functioning mechanical pump (ie there is no mech pump bypass/non-return valve) then the electric pump fuel flow checks need to be taken through the mechanical pump route.

Hope that helps

Regards
Steve