If you taxi really lean you cannot take-off. The engine will not rev up and shudder.
Also it cannot happen if you always put your hand on both levers on t. o.
Also it cannot happen if you always put your hand on both levers on t. o.
Yes: You. And I. But a low-hour student, already saturated with all the taxi procedures and ATC of an international airport might not have his hand on both levers. Even if every instructor told him to do so. In a commercial flying school the head of training has the last word and the two HOTs under whom I have been instructing since 1993 want us to keep the mixture rich on the ground at all times. Whether this is good or bad I don’t know – the point I wanted to make is simply that a typical Pa28 engine can be run on the ground with rich mixture for long periods without any rough running as a consequence.
Still: When I pull the micture of my PA-28-151 Warrior OR my SR22 back to taxi really lean – the engine will not accelerate if you advance the throttle.
I also think that if you consequently teach the method with the hand over both levers, it will become second nature quickly. And it’s better to teach that from the start, because that’s the point where it’s easiest to learn.
The extreme: To my wife the FI said: “Always leave the red knob at max or the engine will go out”. I don’t think that has anything to do with “instructing”. He just thought “ah, stupid woman, artist, better play it safe” …. I guess.
If I taxi my PA-28 full rich for 5 minutes, I almost always have problems at the run-up.
The end of the story:
Yesterday I flew back this airplane after the club’s mechanic had driven up to Hamburg (and back) to inspect it and replace both magnetos. In fact, it would start again after replacing the one you can start on but the other one was still running rough. Apparently it had to do with moisture (?), not fouled plugs.
The aircraft is now undergoing it’s 100h check and I’ll take it over again on Sunday for more flying throughout the entire next week – looking forward to that.
I am starting to think that Slick have some big quality issues with the four cylinder magnetos, I have seen starting issues with slick magnetos on a number of aircraft of late.
One of these aircraft had been subject to lots of troubleshooting and had new ignition harness, new mag switch , new carb and about three new mags. Another aircraft had a number of mags before we got reliable starting performance.
Slick have produced a thing called slick start, this is a starting spark booster that uses battery power to substantially increase the power of the spark during starting. It is my opinion that this device is an admission by slick that the low speed ability of their mags is not up to standard.
A lot of engine related stuff has started to suffer from quality issues over the past ten years, I think that manufactures are being pushed on price at the sales end end and due to “environmental” issues can’t produce parts of the same quality without the price being prohibitive…….. Or may be parts failing inspection sooner is better for business.
When my O-320 Warrior engine started plug fouling on the ground at 2400 Hrs it turned out to be the front camshaft lobe which apparently was allowing it to draw oil in due to the valve being closed too long, or at least that was the theory. It never had any plug fouling or sea level mixture leaning prior to the last 50 hrs of life when it progressively became such an issue that I very nearly had to abandon it on Walney Island, which would have been awkward!
I am starting to think that Slick have some big quality issues with the four cylinder magnetos, I have seen starting issues with slick magnetos on a number of aircraft of late.
Also seen and reported some distributor gears, on which the high voltage “finger” is loose (which could lead to fire at random cilinder).
In general I would say slick is better than TCM, apart from the big 1200 series which are quite good as well. Build quality of factory new and overhauld TCM is quite poor. Maintenance is not to be neglected.
Had a very similar problem last Saturday which still leaves me puzzled as well as annoyed because we missed a great fly in because of it.
Engine: O360 A1D.
Start up was normal and immediate, started at first go. Leaned the mixture immediately after start up and taxied to holding point.
At run up, we got a 200 RPM drop on the LH magneto as well as massive shudder on that magneto. RH Magneto was fine.
We suspected plug fouling and proceeded to do the “burn off procedure” at 2000 RPM with mixture very lean and on both mags.
No effect, same shaking and 200 RPM loss. Aborted the flight and taxied back, as it was on a Saturday no maintenance avialable.
The same day, one of our FI’s heard of this and went to the plane and took off the cowl, confirming that all cables were properly in place. He did another engine run and had no effects whatsoever, apart from an initial “rough running” after start up which disappeared almost immediately. He did a normal mag check, 100 RPM each drop and then proceeded to run up the engine to full MTOP, which it delivered. He went flying the next day and on 2 more occasions since without any further incident.
So my question to the experts here: What the HELL was that on Saturday?
I’m open to suggestions as I hate things I can’t explain.
Do you have an EDM700 or similar?
Spark plug blockages can clear by themselves.
I had this happen at San Sebastian (2005 – since then it cannot be flown to from the UK) and no matter what I did I could not clear it. It was a lower plug, and back then I didn’t carry my huge toolbox… I went back to the restaurant to make enquiries about where I could buy a plug spanner, and then realised I didn’t write down which plug it was, so I started up again to see (it’s obvious on the EDM700; without it you have to remove all the plugs) and it was fine!
The starting (or the previous stopping – one can’t tell) must have cleared it.
Peter,
no, I wanted to get one but have no panel space. I wanted to get rid of the single EGT gauge and replace it with an EDM but apparently that EGT gauge has to be there as it is original equipment. Will have to check again if that is still the case or not.
Very well possible it was something like that. Or that there was some humidity (it had been raining heavily before) which got someplace it was not supposed to and then dried out by the time the FI started up the engine again.
The question in my mind is, what are the steps one can take in such a situation? Do a full power run up? Shut down and restart? We were really miffed about it as we missed a very unique opportunity to visit one of Switzerlands largest airbases. And I really want to know how to cure something like that in case it happens somewhere else.
While we are at it: Which of those analyzers would be your choice? Insight or JP? If it turns out we could throw out that old single EGT, we have a small hole available to put it. Does any of these fit?
