[N941WR]

This is not intended to be an ad but is a serious question I?ve been struggling with.

With the EICommander installed in my plane, I can look over and see exactly what the condition of the ignition is.

The unit?s TDA screen shows me that the ignitions are firing at the correct time, the current advance of each unit, and that my plugs are firing correctly (Not fouled and there is no broken leads).

TDA Screen (Typically the ignition harness graphs are all the same height, this is just a mockup.)

Since I have a fixed pitch prop, is there any legitimate reason to perform a run-up?

 

[Geico266]

To see if the engine will make power before you pull on the runway?

 

[L.Adamson]

To see if the engine will make power before you pull on the runway?

The instrument would probably tell him that, before hand.........I assume.
I suppose you'd know from experience of using it for awhile.

L.Adamson

 

[RV10inOz]

To see if the engine will make power before you pull on the runway?

NO!!! That is what you do on the first part of the takeoff roll. Sitting stationary with the brakes on against full power, not a good idea. Stone damage being the first thing, and jamming more heat under the cowl for no good reason.


The only thing a run up is good for is to verify that you have not had a magneto stolen

In this guys case maybe there is none at all.

Set around 16-1700 RPM, leaned to peak or just a bit more, and do a check looking to see all egt's rise consistently on each mag.

Best time to do a mag check is by running LOP and at altitude.

 

[hydroguy2]

more stuff to check than just mag drop.

oil pressure
smooth and proper linkage operation
sound/vibrations
EGT
proper Fuel flow

 

[L.Adamson]

more stuff to check than just mag drop.

oil pressure
smooth and proper linkage operation
sound/vibrations
EGT
proper Fuel flow

I consider the rest.........a before takeoff check, and on the roll check.

Just no runup for mags, etc.

 

[aerhed]

Prop operation and carb heat also. Vacuum (for jurassic panels). Maybe ammeter check too.

 

[Sig600]

Takeoff is the most critical phase of flight. The airplane must prove it's ability to get airborn, and stay there. Where as landing, if the engine quits the runway is already in front of you.

Your instrumentation tells you all kids of great things about the health of your engine, right now. Doing a run up gives it one last chance to tell you what may happen. Never mind all traditional reasons, but cycling the prop, pulling more fuel through the lines (maybe there is water coming), moving fluid around at normal pressures, all those things idle taxi won't expose.

Is the 45 seconds you save really worth your last chance opportunity to identify a potential failure? With one engine and runway behind you, better be **** sure.

 

[N941WR]

This is good input and food for thought.

Prop operation and carb heat also. Vacuum (for jurassic panels). Maybe ammeter check too.

No vacuum system and I don't use carb heat. (I've found the carb temp goes up just by slowing down.)
I check the ammeter when I flip on the landing and taxi lights.

... cycling the prop, pulling more fuel through the lines (maybe there is water coming), moving fluid around at normal pressures, all those things idle taxi won't expose...

No prop to cycle in my installation and water in the line is a good thought.

more stuff to check than just mag drop.
oil pressure
smooth and proper linkage operation
sound/vibrations
EGT
proper Fuel flow

At the start of my takeoff roll, I always verify oil and fuel pressure and I do watch it rise on startup. The linkage operation I get during warm up, even if I only bring the engine up to 1000 RPM. Sound & vibrations are valid comments. Fuel flow I see when I turn on the boost pump. CHT's and EGT's are watched as the engine warms up, so I know they are working properly.

I still perform a run up, only I do it at 1400 RPM. One of my main reasons for thinking of dropping the run up is to save the prop and reduce heat under the cowl on hot days.

Thanks for the input!

 

[pierre smith]

FWIW

..... The airplane must prove it's ability to get airborn, and stay there. .

Very good reason!

About a month ago, I was taking off in the Air Tractor with 400 gallons of defoliant aboard and during the takeoff run, I lost power...some power, not all of it. I was comitted because the end of the runway was getting close, so we staggered into the air and finished the job. Turns out that my bleed air valve had shucked the diaphragm and I lost 400 ft lbs of torque...it normally pulls 1630 lbs but I was down to 1200 or so.

Best,

 

[terrykohler]

Please Explain

I don't have an engine monitor, so I'm not completely clear. If plugs are fouled, can this be properly assessed without bringing the engine off idle? Not sure I would want to use this approach when attempting to launch into IMC. Even if I abort the takeoff, I've potentially blocked airspace and time for someone else for a problem I could have found before clearance was issued. Finally, I find that many passengers find the runup reassuring -they expect it. Don't want them thinking about what else I may have decided to skip.
Terry, CFI
RV9A N323TP

 

[Don]

Very good reason!

About a month ago, I was taking off in the Air Tractor with 400 gallons of defoliant aboard and during the takeoff run, I lost power...some power, not all of it.

Pierre, I am missing some of your logic. Did you do a run up? If so, am I safe to presume it didn't give you any information to predict the loss of power? If that's the case, you're helping Bill make his point.

FWIW, I always do a run up. My Cherokee has a Jurassic era panel with vacuum and on one occasion over ten years I found fouled plugs. On another occasion the run up failed to find a fuel flow problem. The engine went to idle at about 500' and I found myself looking for a soft tree to set the plane on/in....after a long 10 seconds, the power came back on, I continued my climb out and then landed uneventfully. It took some time to find but the auxillary fuel pump had a leak and would let air in. Not a hint of a problem in the run up...but this doesn't mean I don't believe in doing a run up.

It's a good question to ask and I like the thoughtful answers. My take is the run up is intended to catch problems but I no longer believe it's going to catch them all. I am now pondering if my 21st century 9A will need a run up.

 

[flion]

Aside from many of the other things mentioned before, I set my mixture during my run-up. These are all tasks I don't want to do on the take-off roll, when I am supposed to be flying the plane.

 

[RV8R999]

In addition to all the engine checks for me the run-up is a natural break in the action which provides an opportunity to ensure my cockpit is configured appropriately based on the latest clearances, wind, etc.. and also gives me a chance to surveil the airspace - in otherwords it prevents me from rushing to much to get airborne.. I really enjoy a T/O in which I hardly have to do anything except maintain my airspeed and think about the next 10 steps which are about 10 minutes ahead of me...

my .02

 

[N941WR]

I don't have an engine monitor, so I'm not completely clear. If plugs are fouled, can this be properly assessed without bringing the engine off idle? ...

The EICommander is like an engine monitor but for your Pmag ignitions. it continuously reports on the health of the ignition, including if there is a fouled plug, broken wire, etc.

 

[JonJay]

Plugs can fail or under perform under pressure. A run up to 2000rpm (or whatever your engine manual calls for) builds cylinder pressure. There is a reason that a true spark plug tester uses compressed air to check the plugs. I always "bomb" my plugs at annual to insure they are performing.

 

[flyinga]

I do one runnup a day regardless of the number of legs. I also do a LOP mag check at top of descent. LOP WOT is probably a better ignition check that even a "bomb."

 

[RV8R999]

I do one runnup a day regardless of the number of legs. I also do a LOP mag check at top of descent. LOP WOT is probably a better ignition check that even a "bomb."

could you explain "Top of Descent" at "LOP WOT" please?

 

[John Clark]

With the EICommander installed in my plane, I can look over and see exactly what the condition of the ignition is.

The EICommander is looking at one of the three things (ignition) that a piston engine needs to get you in the air. You need fuel and air to complete the trifecta. Assuming that you are on a proper surface, a 30 second ground run isn't going to do any damage. "On the roll" runups should be reserved for seaplanes and loose surfaces. I prefer to be "heads up" on the takeoff roll, especially in a fairly powerful taildragger.


John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

 

[airguy]

could you explain "Top of Descent" at "LOP WOT" please?

Top of Descent is the transition from cruise to beginning your descent into destination. That's a good point to run an approach checklist.

LOP WOT, or more often written as WOTLOP - Wide Open Throttle Lean of Peak. Throttle is full open, mixture is lean of peak EGT. Very efficient cruising.

I've used the same inflight mag check for years, usually just after settling into cruise speed/altitude. WOTLOP in-flight conditions are the most likely to show an ignition problem, makes sense to do it then.

 

[sstocker31]

It's just good AIRMANSHIP.

 

[N941WR]

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]

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]

Vapor lock?

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]

Agree w/Bill

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]

....
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]

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]

Agreed Gil

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!

 

[aerhed]

I wonder how many CFI's would pass you on a biannual if you didn't do a run-up?

 

[jjconstant]

What?

Old Wives Tales created by flawed but seemingly smart logic!

As I said in my post I have yet to hear an explanation of vapor lock that makes sense to me. My own source of confusion is that I would have thought that after taxi to run-up, run-up and take off, all the fuel would be relatively cool from the tank. This is why I don't understand the vapor lock explanation.

Yet, I have seen accounts of vapor lock causing engine stoppage on a take-off, with fatal consequences. Landed to refuel on hot day, high altitude airport. Are these Old Wives Tales? If so, I would love to hear the cause of the engine stoppage...not to be argumentative, but to try to understand.

All Best

Jeremy Constant

 

[grantcarruthers]

As I said in my post I have yet to hear an explanation of vapor lock that makes sense to me. My own source of confusion is that I would have thought that after taxi to run-up, run-up and take off, all the fuel would be relatively cool from the tank. This is why I don't understand the vapor lock explanation.

Yet, I have seen accounts of vapor lock causing engine stoppage on a take-off, with fatal consequences. Landed to refuel on hot day, high altitude airport. Are these Old Wives Tales? If so, I would love to hear the cause of the engine stoppage...not to be argumentative, but to try to understand.

All Best

Jeremy Constant

Please site an actual accident report

 

[RV10inOz]

Jeremy

The run up will not prevent any vapor lock after take off. Just think about what is actually happening. It may well be folk have crashed, I doubt it but even if they did, the reason will be no boost pump during the take off.

My IO540 after refueling and taxiing to the hangar always suffers from heat soak, I could sit there at the pump and do a run up, but it will still stumble on the way to the hangar. It needs the boost pump on at least until any hot fuel is through the system. Adding more heat does not help.

Adding more pressure does!

First flight of the day....Do a run up, but remember my first post. It really only proves nothing is stolen. Do it leaned to peak rpm for the MP, around 16-1700 rpm, and watch for consistent EGT rises on each cylinder on both mags. This at least tells you if there is a major mag-lead-plug problem. And if done with an all cylinder monitor any problems are easier to find. Cycle the prop ONCE and line up. Pump on, mixture ritch and roll.

The best time to do an ignition system test as in different to a run up, is at altitude, LOP and WOT. So think about it like this. An ignition system test (mags leads plugs) is done in flight WOT and LOP. A Run-Up is a quick ground check all things are there and working as best you can tell on the ground.

DO NOT sit there at full power for ages and cycling the prop several times,sucking up stones, firing them at other planes and damaging your prop while cooking your engine. THAT is bad airmanship.

The next thing to consider is when you do a mag check in flight, do you really know what you are looking for, and when you do see something different do you understand what your EMS is telling you?

 

[RV10inOz]

Sorry Jeremy, did you also want a good explanation of what vapour lock is and why the fuel pump must be used to correct it?

In any case, during the taxi to the runway after the run up, your flow is back to a low level again, and subject to all that heat again, so prone to a vapour lock if the line pressure is low enough.

Hope this helps.

 

[N941WR]

I wonder how many CFI's would pass you on a biannual if you didn't do a run-up?

Why would a CFI not pass me on a biannual?

If the checklist states you don’t need to do a run-up, then one isn’t required, and the CFI couldn’t do anything about it. I am just proposing to operate the aircraft within the parameters it was designed for.

Remember, all the run-up was designed to do was to make sure the ignitions were both operating and to give the pilot a chance to look at the gauges prior to flight. The “run-up” was developed before there where things like EGT and CHT instruments and the only thing in the cockpit was a tach, oil temp, and oil pressure.

BTW, on this evening’s flight, the CHT’s were between 260 and 280*F and the EGT’s were just over 1000*F before I took to the runway after waiting for the oil temps to reach 90*F.

 

[DCat22]

I wonder how many CFI's would pass you on a biannual if you didn't do a run-up?

....before or after you had them prove to you why exactly it mattered on the plane equipped as the OP had?

Not that I wouldn't listen, but the CFI better have some facts to back up what the require and/or teach. I've dumped a few CFI's who had no interest in learning new things....the best will say they don't know and go do some real research.

Anyway, I digress. (And not saying I wouldn't do a runup, either...i've done one 100% of the time. Just that discussion and being able to give your rational for things is important, CFI or anybody. This is an interesting thread.)

 

[aerhed]

Well, I guess that answers my question. The only reason to do a run-up is to please an outdated instructor. Case closed.

 

[L.Adamson]

dumped a few CFI's who had no interest in learning new things.

I've certainly had many disagreements with a number of CFI's. I've come to the conclusion that a lot of them, do not want to go to the trouble of investing the time............into learning new proceedures. It's like my kids, and their texting skills. I'll never learn to be as proficient. These CFIs know the old school methods well, and have to believe that the old ways are time honored skills, that all pilots should abide by.

Just the other day, I mentioned that I don't call "flight service" before every cross country flight. In fact, thanks to online weather, online flight planning, XM Satellite weather, and my SPOT messenger.........I never call flight service anymore. The best that a certain CFI could come up with..........is that I'd be the type of pilot who'd freak out, when doing a BFR with him.......when the plane didn't have a cigarette lighter.

It's like I say...............if a CFI throws your GPS into the back seat, with a smirk on their face, then throw them out!

L.Adamson

 

[Sig600]

Why would a CFI not pass me on a biannual?

If the checklist states you don’t need to do a run-up, then one isn’t required, and the CFI couldn’t do anything about it. I am just proposing to operate the aircraft within the parameters it was designed for.

Try again. If I'm giving you a biannual, and you skip the run-up... I don't care what your checklist says, I'll walk in from there if I have to. We ain't going flying.

Make what ever argument you can conjure up for saving the time... it's the last opportunity to check for ANYTHING wrong with the engine and every supporting system before committing to flight. Is a minute or two really worth it? THAT is the argument you have to make.

 

[RV10inOz]

Few people getting a bit too far off track here.

Sig has a very valid point, it is you last chance to check things are where they should be and working. Not the best ignition test by any means.

Refer my last post

 

[Bevan]

Focus

Perhaps the run up is for the pilot (and his attitude). To positively stop, and tune our brain to what is about to happen. To spend a short time to become one with the engine and the entire aircraft's configuration. To focus, to eliminate any doubt about the current state and configuration of all the "life support systems". Then and only then, head for the runway.

We must remember that successful flight only occurs when we have stacked our team with the right combination of man-made and imperfect mechanics, materials taken from nature, modified for our use, as we prepare to face off in a duel against almighty GRAVITY!. We are not complacent or ignorant (of what it takes to be safely airborne) sitting in the back of some silver tube, with out ear buds in, computers and newspapers, complaining about this and that, completely unaware about what going on around us. No, we are about to attempt to commit aviation. Something that man has only been doing for a relatively short time, yet dreaming about for ever. It deserves all of our attention, skill, knowledge and effort.

Good grief, by all means, take a moment before (and after) each flight. Flying is awesome.

Bevan

 

[Andy Hill]

There is no run-up done on (most) jets, so IMHO the more generic reason above ("frame of mind") do not really apply.

As stated above, the key to me is that the traditional Mag check is required to be done under "power" i.e. for whatever reason, a low RPM Mag check (which can be done after start) is not condiered valid. Is this EICommander really bypassing these laws of Physics? How does it simulate the higher cylinder pressures?

Furthermore, the whole point of a P-Mag is to alter the ignition timing to the optimum - whereas a Mag is by definition fixed. So to me it is more important to test, at a low stress time, that the PMag and dependencies are working over varying conditions e.g. MAP input. How can you test an increased MAP at (near) idle?

Finally, in a typical RV, you have 2 fuel tanks and normally start on one, taxi out (test that tank's feed), then swap and do run ups prior takeoff on the other (tests other tank). If you eliminate the fuel use on the 2nd tank, you need to ensure that you swap the tanks early enough to feed a reasonable quantity of fuel prior takeoff... wouldn't want it quitting at 100' would we

Andy Hill
RV-8 G-HILZ
RV8tors

 

[pierre smith]

.......... No, we are about to attempt to commit aviation. Something that man has only been doing for a relatively short time, yet dreaming about for ever. It deserves all of our attention, skill, knowledge and effort.

Good grief, by all means, take a moment before (and after) each flight. Flying is awesome.

Bevan

...Very well said!

Thanks,

 

[fatherson]

Perhaps the run up is for the pilot (and his attitude). . . . [snip]

I agree with Pierre that your whole post was well said, Bevan. Thank you. I've learned a lot from both "sides" in this discussion, especially that it's a great idea to challenge our long-held patterns of behavior to see if they remain coherent after the challenge. Even if we end up still choosing to do the same thing we've always done, it's beneficial to recall and reinforce why we do it, and to make changes if (and only if) our challenge exposes weakness in our "best" practices.

Thanks for dusting off my thinking cap, everybody.

--
Stephen

 

[L.Adamson]

Try again. If I'm giving you a biannual, and you skip the run-up... I don't care what your checklist says, I'll walk in from there if I have to. We ain't going flying.

I'm looking at this from several directions. Bill R. made the proposal, because of changes in available information regarding the engine. I can plainly see, the reasons why. I think it's a good question.

I assume you're looking at it, from the viewpoint of.... always been doing it.

As far as I'm concerned, changes in proceedure can be made, if it's warrented. We don't have to stick with the "old tried & true".

I've been to flyins/airshows, in which there is a mass exit. No space to do a high rpm runup. Having instrumentation to tell the health of each cylinder certainly beats the old #3 only.....method.

My CFI/BFR wanted me to use carb heat.... from the older Cessna point of view. I refused, and stated my reasons why. I still won't use the tried and true Cessna method, which was derived for Continental engines.

L.Adamson

 

[jjconstant]

Please site an actual accident report

http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20060510X00541&key=1

That's the one that first got me thinking about all this. There was lots of discussion about it on another board. The survivablilty was affected by the shoulder harnesses possibly being loose, but there does seem to be concensus on "vapor lock".

RV10in Oz: please fill in the gaps, but my understanding is that when people speak of vapor lock, what they are referring to is the fuel having been boiled off, typically either in the small diameter spider lines after the mechanical pump or between the boost and mechanical pump. Everyone points to heat soak. Some people put in blast tubes/shrouds around the mech pump, others swear by boost pump, some say it's only a taxi problem...

What I don't understand is the mechanism whereby you can do a start, taxi, runup, no pause, takeoff and have anything but fuel that is as cool as the gas tanks. I even had an engineer friend run the flow numbers based on a few assumptions, the diameter of our fuel lines and the distance from the tanks and he said 20 to 30 seconds of typical startup to take off time and behaviour and you could pretty much be guaranteed relatively cool fuel. This does NOT take into account run-up and then sit around as #5 for take-off on a hot day.

I always use the boost pump for take-off, but it's hard to tell if that was a factor in this accident. I understand the idea of pumping the vapor bubble through with the boost pump rather than trying to suck the bubble with the mech pump, but if the bubble was in the spider, then the mechanical pump should have done the job. Please let me know what I'm leaving out or not clear on

What gets us back to the OP's question and my offering was my thinking that with fuel flowing (not just idling while it heat soaks) more time=more chances of the fuel being cool. Whether that lessens the chances of "vapor lock" is where this discussion has been educational for me. Just to be clear, I'm with you on being suspicious of "vapor lock" being the problem in the take off scenario, but am trying to get educated.

Thanks for your contributions!

Jeremy

 

[jjconstant]

I really like the observation that the run-up contributes to mentally preparing for the flight. It does for me...but I'm certainly no jet - jok

Moderators: if it's appropriate feel free to move the vapor lock portion of this discussion to a different thread...

Jeremy

 

[grantcarruthers]

http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20060510X00541&key=1

That's the one that first got me thinking about all this. There was lots of discussion about it on another board. The survivablilty was affected by the shoulder harnesses possibly being loose, but there does seem to be concensus on "vapor lock".

RV10in Oz: please fill in the gaps, but my understanding is that when people speak of vapor lock, what they are referring to is the fuel having been boiled off, typically either in the small diameter spider lines after the mechanical pump or between the boost and mechanical pump. Everyone points to heat soak. Some people put in blast tubes/shrouds around the mech pump, others swear by boost pump, some say it's only a taxi problem...

What I don't understand is the mechanism whereby you can do a start, taxi, runup, no pause, takeoff and have anything but fuel that is as cool as the gas tanks. I even had an engineer friend run the flow numbers based on a few assumptions, the diameter of our fuel lines and the distance from the tanks and he said 20 to 30 seconds of typical startup to take off time and behaviour and you could pretty much be guaranteed relatively cool fuel. This does NOT take into account run-up and then sit around as #5 for take-off on a hot day.

I always use the boost pump for take-off, but it's hard to tell if that was a factor in this accident. I understand the idea of pumping the vapor bubble through with the boost pump rather than trying to suck the bubble with the mech pump, but if the bubble was in the spider, then the mechanical pump should have done the job. Please let me know what I'm leaving out or not clear on

What gets us back to the OP's question and my offering was my thinking that with fuel flowing (not just idling while it heat soaks) more time=more chances of the fuel being cool. Whether that lessens the chances of "vapor lock" is where this discussion has been educational for me. Just to be clear, I'm with you on being suspicious of "vapor lock" being the problem in the take off scenario, but am trying to get educated.

Thanks for your contributions!

Jeremy

May have been vapor lock, not saying it doesn't happen, but it vapor locked due to a pump failure and inadequate fuel system pressure. In this instance, a run up may have made the situation worse, not better.

Serious question, what's the fuel capacity of the whole fuel system fire wall forward? Whats fuel flow at a typical 1600-1700 rpm run up? Can any fuel flow of cool fuel overcome a ~200 degree cowl environment.

I have mags and do a run up. Realistically the first few hundred feet of the TO roll is when I really make the go, no-go decision though.

 

[Sig600]

I'm looking at this from several directions. Bill R. made the proposal, because of changes in available information regarding the engine. I can plainly see, the reasons why. I think it's a good question.

I assume you're looking at it, from the viewpoint of.... always been doing it.

As far as I'm concerned, changes in proceedure can be made, if it's warrented. We don't have to stick with the "old tried & true".

I've been to flyins/airshows, in which there is a mass exit. No space to do a high rpm runup. Having instrumentation to tell the health of each cylinder certainly beats the old #3 only.....method.

My CFI/BFR wanted me to use carb heat.... from the older Cessna point of view. I refused, and stated my reasons why. I still won't use the tried and true Cessna method, which was derived for Continental engines.

L.Adamson

Valid points, but I'll defer to the real question...

Tell me what you gain by not doing a run up as routine procedure?