What Does It Mean If .....

[Big Pistons Forever]

Personally I think that understanding of what the engine is telling you is rather weak in flight training and in GA in general. I am posting some scenarios in order to encourage some critical thinking. So what does it mean if:


1) You are flying a Continental powered airplane and when you turn the ignition key to start the engine there is a high pitch whine followed by the prop giving a big jerk and then rotating normally

2) Right after start you notice that the ammeter is indicating full scale charge

3) Right after start the engine runs quite rough but over a few minutes smooths right out.

4) During the run up when you select one mag there is no drop in RPM

5) During the run up when you select one mag you get a 75 RPM drop but when you select the other you get a drop but it is very small maybe only 10 RPM

6) During the runup the ammeter is indicating minus 10.

7) When you apply carb heat there is no change in RPM

8 ) When you apply carb heat the RPM increases

9) With the carb heat applied you lean the engine and the RPM immediately drops as you start leaning.

10 ) On a very cold day you do a fairly long climb and when you level out you see the oil temp almost at the redline.

11) During normal cruise on an average + 15 C day you see the oil pressure is at the bottom of the green arc and the oil temp is at the the top of the green arc.

[digits_]

I predict this topic will run for 15 pages and then get locked, in about 8 days.

I'll give it a try:
1) Starter issue caused by weak battery? Rarely fly a continental. Why is that important for the question?
2) Battery was very weak. Should stop charging soon. If not, shut off your alternator.
3) Some dirt on your spark plugs or contamination/moisture in the lowest part of the fuel system right before it enters the engine. Didn't drain properly?
4) Broken P-lead
5) A broken spark plug on the other side
6) Alternator off or broken, although that should have been noticeable earlier
7) Broken carb heat cable, or stuck carb heat valve, either open or closed
8 ) Icing in the carb or wrong mixture setting.
9) It's probably a cold day.
10) Frozen oil cooler
11) You might get to practice a real precautionary landing soon!

[photofly]

1 is a failing starter adapter. The whine is the motor freewheeling, then the spring catches, winds up, grabs the shaft and jerks the crank and prop, and starts normally.

Speak to PilotDAR

Lycoming starters have different problems, but since they’re at the front of the engine they are much easier to reach.


Here’s one from me:

12: engine runs continuously rough in cruise except when the carb heat is applied. No, not carb icing, something else.

And one more:

13: in cruise there’s a clattering noise and a slight increase in rpm. And a funny smell (when it happened to me.) Where should you look next?

[Big Pistons Forever]

Photo you are spot on re my number 1. If this happens you need to get the starter adapter repaired immediately. Total failure of the adapter can result in pieces of metal in the engine which when distributed in the oil can cause a very expensive early engine overhaul.

I will bite on your Number 13

Broken alternator bracket. Confirm with a discharge on the ammeter and/or low volt light. The smell is the drive belt being chewed up. The slight rise in RPM is a result of the alternator load being removed from the engine and the chattering is the alternator bouncing around lose on the engine

[digits_]

1: Is that one related to the continental issue where the starter might not disengage and screw up expensive things?

12: mixture set too lean?

[RedAndWhiteBaron]

I think digits is correct on 1-10.

11 I think would be a broken or failing oil pump
12 Sounds like a partial air filter blockage to me
13 Not sure? Sounds like the alternator pulley may have seized and fallen off? That smell could be either bits of the belt burning up in the engine or a stuck belt that's getting burned up on the crankshaft pulley (but that should cause a drop in RPM). Look at the ammeter. Or perhaps it's just broken now, all the pulleys are still on, but without the load, you have a higher RPM, but I'm not sure what the smell would be in that case. I'm betting the alternator belt is in bits and pieces now and slowly burning up somewhere.

[Big Pistons Forever]

14. You turn on the master and the prop starts rotating

[digits_]

12 Sounds like a partial air filter blockage to me

Yes! Good point, much more likely.

[RedAndWhiteBaron]

14: Stuck or short-circuited starter solenoid.

15) After an hour of cruise, you suddenly are limited to 2100RPM after running at 2400 since you levelled off. Carb heat is ineffective. Where should you look?

16) Same - but this time, after an hour of cruise at 2400RPM, RPMs drop slowly, and level off at 2100. Again, carburetor heat is ineffective.

[pelmet]

I think digits is correct on 1-10.

I'd say at least one is wrong. But the question is......

Which scenario between 1-10 is applicable to this video.....

https://www.youtube.com/watch?v=7ohsVvYbAaQ

[photofly]

13: a broken alternator belt will do it: the clatter is the belt being thrown and the smell is the rubber melting all over the exhaust manifold.

[Big Pistons Forever]

13: a broken alternator belt will do it: the clatter is the belt being thrown and the smell is the rubber melting all over the exhaust manifold.

The one time I just had the belt break I was lucky and it was just thrown clear. The other time started with a broken alternator support arm. There was quite the commotion from under the cowl as the belt was still attached and caused the alternator to flail around until the edge of the drive pulley cut the belt. This of course happened IFR and in the goo

[digits_]

16) Same - but this time, after an hour of cruise at 2400RPM, RPMs drop slowly, and level off at 2100. Again, carburetor heat is ineffective.

Fix your friction lever?

[photofly]

I think digits is correct on 1-10.

I'd say at least one is wrong. But the question is......

Which scenario between 1-10 is applicable to this video.....

https://www.youtube.com/watch?v=7ohsVvYbAaQ

Sticky valves is 3 - aka "morning sickness".

[photofly]

2 can also indicate a Lycoming engine with starter stuck on engaged. There's also an unusual running noise. Shut off quickly, or be ready to buy a new starter motor.

9 means your carb needs attention: the mixture isn't rich enough. However I have an O320 with barely much mixture rise, and on chatting to Marvel-Schebler tech support, this model of carb is designed to run lean, and doesn't show much on leaning.

5 is a mag whose timing is wrong, or which needs overhaul.

5) A broken spark plug on the other side

A dead plug will give you a huge mixture drop and very rough running (especially on 4 cylinders) when running on one magneto.

17: if you do suspect a dead or fouled plug during your run-up, and you don't have a digital engine monitor, what's the quickest way to find which plug to pull?

1 8: If you have a digital engine monitor, what indications would tell you instantly that a plug had died in flight, even before you reach for the ignition switch, to check?

12: mixture set too lean?

Nope... anyone else want to guess?


19: In a fuel injected engine, suddenly a very low analog fuel flow indication, but simultaneously a very high digital fuel flow indication. How urgent is this situation?

20: an abnormally high oil pressure indication in flight (temperature normal).

[RedAndWhiteBaron]

16) Same - but this time, after an hour of cruise at 2400RPM, RPMs drop slowly, and level off at 2100. Again, carburetor heat is ineffective.

Fix your friction lever?

Hah! That would do it, I didn't think of that. However - in my theoretical, 2100RPM is now all the power the engine can produce.

[Bede]

This one happened to me recently.

Gusty surface winds. After 2 hr flight at altitude on decent get a burning plastic smell. Then goes away as quick as it starts. Happens 2 more times.

Electrical system checks out ok.

[RedAndWhiteBaron]

This one happened to me recently.

Gusty surface winds. After 2 hr flight at altitude on decent get a burning plastic smell. Then goes away as quick as it starts. Happens 2 more times.

Electrical system checks out ok.

You missed the fact that you sucked a mylar balloon or pastic bag into the engine cowls?

[RedAndWhiteBaron]

17: if you do suspect a dead or fouled plug during your run-up, and you don't have a digital engine monitor, what's the quickest way to find which plug to pull?

1 8: If you have a digital engine monitor, what indications would tell you instantly that a plug had died in flight, even before you reach for the ignition switch, to check?

19: In a fuel injected engine, suddenly a very low analog fuel flow indication, but simultaneously a very high digital fuel flow indication. How urgent is this situation?

20: an abnormally high oil pressure indication in flight (temperature normal).

17: Spark plug tester?
18: The cylinder head with the dead plug will be cooler?
19: Seems like a problem with the injectors? Not sure how urgent that is.
20: Oil filter screen is blocked.

[photofly]

17: Spark plug tester?

Hard to wield one at 120 knots, but a digital engine monitor will show you the instant a plug dies. Hint: what does the engine monitor show (for all cylinders) when you test the mags during the run-up? The same indications on one cylinder in flight show a cylinder firing on only one plug - but what are those indications?

18: The cylinder head with the dead plug will be cooler?

That's the answer to 17. Run on the rough mag for three or four minutes at 1800 rpm. Then shut down and hold a damp rag against each cylinder head in turn. The one that doesn't sizzle is the one with the defective plug. Then trace the lead to the rough-running mag to find which of two plugs.

After a horrible bout of not being able to clear a fouled plug using the technique in Q18, a very wise A&P/IA did the sizzle test and worked out that the temperature probes on the cylinders weren't wired in the right sequence, so it wasn't cylinder 4 that was running on one mag as displayed on the engine monitor, it was actually cylinder 3. Two minutes later the correct plug was cleaned and the engine ran fine.

20: Oil filter screen is blocked.

That should give you a higher oil temperature too, although there is a filter bypass. So no, not that.

19: Seems like a problem with the injectors? Not sure how urgent that is.

Hint: it's extremely urgent, and you're likely to die (yes) within a few minutes unless you're able to get on the ground anywhere.