Are Run up checks really needed ?

by Glenn Martin in 912iS Technical Questions 9 years ago

Hi All,
I would be interested in your thoughts.Originally a run up check was to check whether both air gap magnetos were working when under load. Given the unreliability of these ancient devices it is a good idea.

When we moved to electronic ignition it was still a good idea to check that both ignition systems were working.

Now we have duel ECU which automatically and continuously monitors this and warns us with a light of an issue is a "run up check" really a good idea ? or is it just "habit" or "tradition".

I do not believe you can actually turn off the ignitions anyway as the other channel just keeps it running, so what if anything are we checking on a run up check ?

Regards

GlennM

Re: Are Run up checks really needed ?

by Roger Lee » 9 years ago

Roger Lee

126 5.13k 4.58k

Hi Glenn,
No more simple magneto's just a complicated electrical system.
With the 912is engine this checks the lanes (A & B ) to make sure they are both operating and functioning normally. It makes sure that if you have a Lane failure the other will function properly and that both ignition systems are functioning properly.

You sure you don't want your magneto's back? ;) :lol:

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Are Run up checks really needed ?

by Glenn Martin » 9 years ago

Glenn Martin

3 281 800

Hi Roger,
thanks for the reply..no magnetos thanks it is the 21st century !

I know suggesting this is almost heresy to Pilots but I do want to understand the system in greater depth.

I still do not understand the need... you say it means I know both Lanes are working....

But I already know that within 30 seconds of running the engine as the ECU tell me via the lights going out. The ECU will also continuously tell me of issues throughout the flight, which is far superior to a single test and "hope that it stays good" as we had with the old "left right test".

As a backup to the lights (on/off or blinking) I also know that BOTH lanes are working as the EIS signals are working and if......

Lane A was NOT working I would not get Oil temp and Oil pressure readings.

IF Lane B was NOT working I would not get Coolant/Exhaust and Ambiant temps and Pressure and TPS.

The RUN UP tells me NOTHING I already do not know. It does NOT check ignitions as either computer (Lane A or Lane B) runs BOTH ignitions, so turning off Lane A or B does NOT drop back to a single ignition. We do NOT need an ignition check as the ECU is doing that continuously for us every rotation of the engine for the entire flight.

The run up confirms that both lanes are working "at that instant in time ONLY". Whereas the ECU continuously monitors so we actually have a "continuous run up check"

This is of course far better than just one point in time.

So unless I have misread the manuals and have missed something fundamental the "run up test" is pretty much a historical anomaly. Naturally I have no issue with people doing it ..if it makes them feel better, I would just like to know ONE thing it tells me that I do not already know or is not already being continuously monitored by the computers on my behalf ??

Cheers :)

GlennM

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Re: Are Run up checks really needed ?

by Rob Seaton » 9 years ago

Rob Seaton

3 1.32k 240

Hi Glenn,
one ignition set and one injector set is shut off with the Lane check so you are performing a worthwhile check. you don't see a big RPM drop as the ECU switches to Power Mode (mixture goes rich) and the other injectors go into double-time mode (fire twice each power stroke to make up for the "dead" injector)

You are correct for the generators: when you tune off Lane A you are not necessarily turning off GEN A, the ECU decides what is the appropriate Gen to turn off.

For the Lane check: you are double checking the system and that the warn light and switch are working. (I know, you already know they are working but its comforting to verify this before taking off)
Rob

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Re: Are Run up checks really needed ?

by Glenn Martin » 9 years ago

Glenn Martin

3 281 800

Hi Rob,
thanks, at least that is something that is being checked !

But it does sound like we are close to closing off this part of aviation history. I have been involved in another aviation development where we deliberately designed a power on self check of all systems by the computer thus removing the need for Pilot input. From my Boeing 777 pilot friends this is standard in modern aircraft... no left right checks on a 777 or 787 !

In fact my LSA pilot startup checklist is apparently longer than the 777 one !

Thanks again

GlennM

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Re: Are Run up checks really needed ?

by Joe Harrington » 9 years ago

Joe Harrington

1 26 0

Hi Rob,
I am with Glenn on this one. What is the need for checking (cycling) Lane A & B? Does not the warning (fault) lights illuminate if there is any problem? Can you give me an example where neither of the lights would be on but you might find something amiss from cycling each lane switch? It might make the traditionalists feel better, but are we accomplishing anything? Just asking...
Thanks,
Joe

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Are Run up checks really needed ?

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