On Saturday evening I took one of the club’s PA-28 to Hamburg to stay here for a few days. I had preponed by 1-2 days because worse weather was to be expected on Sunday and Monday (it ended up being rather nice, still). In any case, the Saturday evening flight was beautiful – I arrived over the city of Hamburg with a beautiful light cast over the cityscape by the setting sun. I was asked to circle overhead the Aussenalster to give way to some Airbus on final. I had the GoPro running on a suction cup mount, however I had failed to empty the memory card and the film just terminates BEFORE I got to this memorable point of the flight. The flight was about an hour at 5500 ft, with the engine leaned to about ROP.
On Sunday (which turned out to be surprisingly sunny, if a bit gusty) I was going to take some friends on a short local trip. After a rather complex taxi procedure from the GA apron (crossing two active runways, the main apron and multiple frequency changes between Apron and Ground), we reached the holding point at E for Rwy 15.
(Short question here, not the main point of discussion: I find it ambiguous who to call first at Hamburg if departing VFR from the eastern stands of Apron 2 – see plate below. Do you call up tower directly as this area has been assigned to TWR? Do you taxi on your own to the green border and call Ground?)
But what I really want to discuss is what happened next:
During the run-up, for the first time since I’ve started flying, I experienced what was in my view VERY severe rough running (beginning at 1500 rpm). Then again, I wouldn’t be able to tell extreme rough running from not so extreme rough running for a lack of practical experience. In any case, the aircraft was shaking quite substantially and the engine certainly didn’t develop power as usual. I was a bit under pressure after the taxi marathon and lots of airliner traffic generally, so I did not go into problem solving mode as calmly as would have been mandated. In any case, I tried a couple of things – runnning the engine at higher rpm and leaning a bit to potentially clear fouled spark plugs, but as the vibration was quite substantial, I did not dare to do this with throttle fully open and for an extended period of time. So IF the spark plugs were fouled, I think I did not do this long enough and not with sufficiently high RPM. It would be a plausible solution for me because the taxi procedure took quite a while and I was running quite (not fully) rich on the ground. I checked each mag individually and on the first check, thought I’d noticed smoother running on one mag but on a second check, didn’t anymore. I admittedly entirely forgot about carb ice (in the air, I would have thought of it I guess – but it didn’t occur to me on the ground). I eventually aborted the take-off, to the nuisance of ATC having to taxi back on D rather slowly. The engine ran smooth enough at RPMs around 1000-1200, but whenever I added more throttle, it became very rough again so I decided not to and told ATC I wasn’t able to taxi faster.
I then spoke with the club mechanic yesterday who told me that I should have followed through with the high RPM setting for a minute or so and that I wasn’t going to make things worse by doing that. So I went back to the aircraft last night to try this.
Unfortunately now, the engine doesn’t fire up at all. I first made a normal attempt as per POH (this airplane has a modified fuel system due to it running on MOGAS. The procedure calls for one of the (two redundant) fuel pumps to be on for three seconds, then off for start-up). The starter cranks fine, but the engine doesn’t come to life. I then executed a second attempt after priming for three seconds. I then tried several variations after breaks to cool off the starter (switched tanks, less throttle pumping, more throttle pumping, one more time priming, once with fuel pump on, pumping throttle a bit before cranking) with no positive result. After some time, I did more attempts with the club’s “general manager” on the phone. He suggested the engine might be flooded (overprimed? possible, after multiple attempts with priming?). He asked me to check outside for leaks. I found a puddle of liquid around the nose wheel (a bit aft). Is this where fuel would appear if the engine has been flooded? When I picked up some liquid on the finger, it looked like oil (black) but could it have been fuel colored by the “dirt” on the tarmac? I’d say it smelled more like fuel than oil, but I’m not sniffing the stuff often enough to tell with absolute certainty.
I then tried one “start up with overprimed engine” procedure, i.e. full throttle, mixture idle, prepared to pull back the throttle and advance the mixture should the engine fire, but it didn’t.
That’s it for now – I expect to be on the phone with the club mechanic today and drive out to the airport again tonight (there goes my evening planning in Hamburg this week).
I’m sharing all this because I’m looking for a more educated idea of what might have gone wrong, what’s going on. I’m wondering – is this based on some mishandling from my side? Could I have prevented this? What can I still do as a pilot before the plane has to go into maintenance here in Hamburg, which of course would be a hassle.
Do you always taxi with the mixture sigificantly leaned? Doesn’t sound so. Just pulling the mixture by an inch or so does not help any.
This probably caused your problem. I guess your plugs are totally fouled.
Have someone remove and clean them. Any mechanic can do that.
Is it a PA-28-151/161 Warrior with an O-320 engine?
I have one of these, and I can tell you that prolonged taxi with the mixer in a too rich position makes my plane UNFLYABLE. You have to pull the mixer bacsk almost to where the engien starts coughing and leave it there until take-off. I even do the run-up in a very lean position – and you will never forget it there, because the engine will not rev up with the mixture too lean.
When it happened to my Warrior a couple of times when I wasn’t paying attention I sometimes managed to burn the dirt away with 2000 rpm and a lean mixture … But it can take a while and you have to be careful to not overheat the engine on the ground. Other than that: Remove spark plugs and clean them. If it doesn’t start that’s your only option anyway.
Do you always taxi with the mixture sigificantly leaned? Doesn’t sound so. Just pulling the mixture by an inch or so does not help any.
In training, we pulled the mixture back somewhat – but not to any specific point as you would do in flight.
Nowadays, with different club and charter aircraft flown, I’m trying to follow their varying checklist procedures.
Is it a PA-28-151/161 Warrior with an O-320 engine?
No, sorry for being unspecific. It’s a PA-28-181 with an O-360.
Nowadays, with different club and charter aircraft flown, I’m trying to follow their varying checklist procedures.
You should rather do what is right.
I have never seen anything as bad as club / school made checklists and “club procedures”.
Anybod who just told you to “just pull it
out a bit” didn’t have a clue.
You should rather do what is right.
I can see the beauty of that argument. It obviously becomes easier to do that as experience (such as this week!) grows.
To a certain extend though, if I rent an aircraft (or something else) from someone, I’ll follow their procedures as long as it is not in conflict with what I consider safe and right (see line above).
I.e. the POH of the PA28-181 I did the check flight on (like any other) tells me to start the engine on one mag. In the aircraft itself I find a placard with two exclamation marks urging me to start on both mags. So I’ll do that…
Taxi at peak EGT, nothing else. If I do to my plane what you did to yours, the engine would die. The only time to run full rich is during takeoff and maybe in short final (I don’t).
It may or may not be the plugs.
IME, every case of a fouled plug (several) was a bottom plug, never a top one. A real bugger because access to the bottom ones needs the cowling removed, which needs the prop spinner removed (unless you are a Grade A bodger and the customer will not notice the damage). So I have never had both plugs in any cylinder fouled.
But I guess it is possible.
The top one should clear fairly easily using the traditional approach of setting ~ 2000rpm and leaning to peak EGT while running with the ignition switch on either BOTH or on the other plug. This won’t work if both plugs are fouled because, ahem, there won’t be any combustion to start with 
and then at least the top cowling has to come off.
There is a POV that departing with one bunged up plug (i.e. all cylinders producing power) is OK. I know a pilot of a twin who had a persistent problem with bunged up plugs and he did this on most departures. I have done it just once… but never fly with a suspected bad magneto.
I agree re taxi with the mixture leaned to the point where the EGTs start to drop off (i.e. LOP) or, if you have no EGT indication, to the point where the RPM peaks and then starts to fall. But I could taxi full rich if I forgot to lean, and AFAIK most pilots do that. It is only the “educated / pilot forum” community that knows about this. My bunged up plug episodes were never following a full rich taxi. They seemed to be just random (Champion RHM38S iridium plugs, back then, now I use the Tempest ones). My PPL training (Shoreham, 2000-2001) never mentioned leaning, at any phase of flight, and clearly this type of operation is widespread. What I can tell you however is that if I do the 50hr service after running the engine full rich, the plugs are so completely covered in crap that I can hardly see the insulator 
It’s hard for me to offer a good suggestion, but it does seem odd that the engine won’t start at all now. I have never seen such a thing. Not even one cylinder firing. I would leave the plane parked and let the school sort it out. It could be something serious. But then my attitude to risk is, ahem, not the same as somebody else’s.
BTW I have never heard of starting on one mag. I flew a -181 (G-SARA; back then a shagged old heap in which I got my then GF to copy every frequency to a handheld radio, just in case but it flew really well) for about 50hrs. It is I believe the case with some engines that only one of the two mags produces the correct timing for starting, but the “wrong” spark is just wasted and doesn’t stop the engine starting.
O-360 in an Archer will behave vey much the same as the O-320, that’s basically the same engine with a little more displacement.
Forget all those checklists form the 70s (when my father learned to fly in 1969 he was told to never lean at all below 5000! – and some CFIs still distribute that B.S. Like Achim I ONLY use full rich for takeoff – or fo go-around. I also leave the mixure in the lean position and will only push it to full rich in case of a go-around. Taxiing only a “little lean” will foul the spark plugs in most engines.
Patrick, I suppose you are running out of options, since by now your battery is probably almost dead. Can’t exclude there is something else seriously amiss unless you pull the plugs, clean then and the engine runs well after that.
I was never taught to lean during taxi either, but did learn how to lean during run-up to clear the carbon fouling. It was not until I got to the US I was told leaning during taxi , especially on warm summer days, was a good idea.
I do not bother about. EGT during leaning for ground operations since the EGTs are outside the scale. I just lean to peak RPM which is almost the same.
