Why do a run-up?

[sstocker31]

It's just good AIRMANSHIP.

[N941WR]

Originally Posted by sstocker31

It's just good AIRMANSHIP.

I don't understand this comment.

If the instrument tells me that I have a good ignition, fuel flow is good, CHT & EGT's are up, there is no prop to cycle, what is to gain by performing the run up?

Granted it is tradition but with the P-mags feeding their status to the EICommander and a full EMS providing vital engine statics what is to gain from the run up?

[sailvi767]

I can't think of anything a runup would tell you in your aircraft that would not become apparent in the first 100 feet of the TO roll. My limiting factor for takeoff is normally getting the oil temp up and a runup helps with that. I worry about the dual lightspeed setup I have. I don't have the ability to monitor it like you can so I like to carefully check both.

George

[L.Adamson]

Originally Posted by sstocker31

It's just good AIRMANSHIP.

Last year, I was told by an instructor....................that setting my OBS's (nav radios) before every cross country flight, was basic "Airmanship". And that if I wasn't doing so............I shouldn't even be flying. At the same time, he was relegating the GPS as a backup, and that I should still be triangulating VORs for the "more direct" trips, that I setup, thanks to GPS.

There were two problems though. No nav radios, and lot's of mountain flying where VORs are line of sight. IMO, what's constitutes "airmanship" can change over the years, as we progress with new technologies. I sure, that with the advent of VORs, that some thought they were cheating too.

L.Adamson

[jjconstant]

One thing a runup ensures is that the fuel your engine is seeing has not been preheated...time and power ensure that you're burning fuel that has just been in the tank. I have yet to hear an explanation of a vapor lock incident that makes sense to me, but on a hot turnaround a runup should theoretically lessen that problem.

Jeremy Constant

[John Collier]

Bill, I'm in the same boat as you...

You are not doing the run-up at takeoff power...my EFIS flags engine parameters that don't meet takeoff requirements...so...

My run up is around 1300-1600 RPM...check the PMags (3 seconds)...cycle the prop (5 sec)...and give the engine a few seconds to indicate normal temps/sounds and clear any vapor in the fuel lines.

So yes...I do a very quick run up...but I'm not the guy who is running up for 30+ seconds at a high power setting and running up the CHTs...just doesn't feel right for me.

YMMV.

[az_gila]

Originally Posted by John Collier

....
So yes...I do a very quick run up...but I'm not the guy who is running up for 30+ seconds at a high power setting and running up the CHTs...just doesn't feel right for me.

YMMV.

But there is a debate, and lack of official Lycoming numbers IIRC, on what the minimum CHT should be for take off.

A run up does help raise the oil temp and CHTs, even in Tucson...

[N941WR]

Originally Posted by az_gila

But there is a debate, and lack of official Lycoming numbers IIRC, on what the minimum CHT should be for take off.

A run up does help raise the oil temp and CHTs, even in Tucson...

Gang, I'm not talking about dragging the plane out to the end of the runway, firing her up, and then blasting off.

If you sit on the ground, warming the oil to at least 90*F then the CHT's are also going to come up. Also, what about a prolonged power off (OK, at idle) glide into the pattern and touch down? Then your CHT's will come way down. Say you do this and then have to do a go-around? What's the difference?

Could one of our Alaskan builder's answer a question for me? In the winter, how warm does your oil have to be before you take off?

[John Collier]

The ole skyview is flashing in my face until 100F. Being able to program what I want in the EFIS helps ensure everying is up to temp. That, plus my long taxi out at KRYN

I think Bill's point is that your engine equipment and engine instrumentation should dictate your runup technique.

Ill often do my 10-15 sec check prior to rolling...its an opportunity to notice a loose oil door, missing cowling hinge, bad EGT, CHT, or whatever might come loose or become noticable with more power. FWIW...i caught a partially blocked fuel injector with EGT/CHT on "run-up".

So run up for me yes...something around 1400-1600 (I dont waste the time trying to chase a number)...check PMag for self gen, cycle prop, check engine inst...done. The rest of my checks are done before the rwy...lights, belts, canopy, trim, fuel, etc.

[RV10inOz]

What?

One thing a runup ensures is that the fuel your engine is seeing has not been preheated...time and power ensure that you're burning fuel that has just been in the tank. I have yet to hear an explanation of a vapor lock incident that makes sense to me, but on a hot turnaround a runup should theoretically lessen that problem.

Jeremy Constant

So by that logic, after you have done your runup and pumped a heap more heat in under the cowl and you taxi to the threshold, how do you think that fuel is in your lines ? Same? Worse?

Old Wives Tales created by flawed but seemingly smart logic!