The real deal

[Fizt4hire]

So, I was up practing 180 autos yesterday, and we went from a simulated to actual failure with the twist of the throttle. Right after entering I was rolling throttle down and around 2400 rpm (flying a 300) I see the engine tach spike and drop to zero and the map shoot up to ambiant pressure. The quiet, while peaceful, was also a disturbing indicator that this was for real. The CFI caught it as well and as soon as we were established I handed off controls. He had me watching the gauges so he could keep his eyes outside, and the resulting touchdown was softer than most hover autos. The end result was beautiful, no damage or injuries, right on centerline and less than 50 ft. from the spot we were aiming for!

 

Later it was discovered that we had only been running on 3 cylinders due to a clogged injector, and that really got me to thinking. Prior to the manuver, we had done an offsite with a high performance takeoff. I had noticed we were lacking in power on the liftoff but other than that one manuver there was no indication of a problem. Now that I'm safe on the ground it's nerve racking to think about what could've happend if that little timebomb went off at any other point during the flight. At our airport there are powerlines (of course) on the approach end, and the surrounding area leaves little in the way of nice and open forced landing sites. It was pure luck that our problem didn't manifest itself until I was reducing power in a manuver that was a perfect setup for an engine failure.

 

Anyway, since then I've been running the scenario over and over in my mind, and all that basic stuff that gets drilled into the aspiring pilot's head since day one takes on a whole new realevance after a real emergency. Always have that forced landing site in mind, know what the wind is doing, keep everything within limits, and for the love of god, eyes outside! We had the good fortune of already being in a position to auto to the runway (which is a prime example of why autos are practiced within reach of the runway). As things happend so fast, I could see how an unexpected failure could end very badly. The CFI had done his share of full downs, but this was his first engine out landing as well. Long story short, always be ready for the unexpected. Next time I wont have someone there to save my ass.

[adam32]

I'm surprised you couldn't hear the engine missing or at least running rough... ??

[Fizt4hire]

Funny you mention that, this was a new (well 200 hrs on another a/c) engine, and it was running waaayyy smoother than the previous one. Aside from that one high power takeoff, seemed like it was purring like a kitten...

[PhotoFlyer]

I'm surprised you couldn't hear the engine missing or at least running rough... ??

 

The engine is turning at a relatively high RPM, so the inertia of the rotating components keeps it going without roughness when the cycle gets to the dead cylinder. Essentially the engine doesn't need that cylinder at high RPM. Of course this would cause reduced power available. But the engine is turning so fast that it would be difficult to hear it missing. At low RPM the engine would run rough, if at all, because it needs that cylinder more since there is less inertia in the system.

 

I hope that made sense.

 

Glad everything turned out ok. My own engine failure in the 300 turned out similarly, except we landed on a slope in a wheat field. Luckily the slope (couldn't see it through the wheat) wasn't too much for the helicopter.

[helicopterdan]

An old-timer I got to fly with told me that the majority of the engine failures he experienced were from cutting the throttle during an auto. He flew Enstroms.

[adam32]

An old-timer I got to fly with told me that the majority of the engine failures he experienced were from cutting the throttle during an auto. He flew Enstroms.

 

I heard of that happening in 300's when the idle is set to low.

 

PhotoFlyer, yeah I kinda get what your saying, but it seems strange that when 1/4 of your cylinders aren't working I would think/hope it would be somewhat noticeable...?

[Mikemv]

To all, let me ask you if in training or real world ops you do a magneto check before coming out of a confined area or practicing a max performance take off???? Piston or turbines, most engine failures will come on a "Power Change" When I operated Hillers & Bell 47's for Park ops or training, I always did a mag check! Good job on this one guys, good luck, be safe, Mike

[mechanic]

Like Photoflyer said, at higher rpm its harder to tell on a multi coil or fuel injected engine. I work on utility engines that have separate ignition coils, time to time I get customers that bring their machines in saying its running weak. They can't tell the difference in exhaust sound running on 1 cyl vs. 2 cyl's and most of the time the owner has several hundred hours of running these machines and still can't tell. The problem with the coil or plug fouling on a carb'd engine is the dead cylinder is still drawing in fuel into a cylinder that's not burning. Your engine oil starts to get diluted from the gas wiping down the cylinder walls. If you clog a fuel injector that cyl is just pumping mostly air. A fuel injected engine can also wash the cyl too if the ignition source is lost... I just see more carb'd engines.

 

When you loose total spark or fuel on one cyl with these type of setups, that cyl basically turnes into an air compressor. There was a company that had a conversion for VW engines to turn them into a air compressor. Ya, you swapped cyl heads on the left bank to make those cyl's pump air, installed a aftermarket intake on the right bank. So you had left bank- 2 cyl's pumping air and the right bank rank the other 2 cyl's for power.

 

Now you are probably totally confused! he he..... Or not.

[ohman]

my pickup "popped" a spark plug the other day, so I was down to 3/4 power, and when I looked under the hood, the engine was jumping around as far as the motor mounts would stretch.

fortunately, I only had to pull to the side of the road.

 

that said, I guess I can understand how a helicopter's torque in an auto would provide the oomph to get through the bum cylinder.

 

congrats on the new addition to the log book FizT4Hire