Vic
>>>> there are loads of accidents with aircraft not reaching the runway because the engine would not make power the moment you needed it
Actually that’s a very rare thing to happen, i cannot remember one such case. Leaving the mixture in the wrong place does not qualify as an engine failure to me either.
But as i said: If those were your criteria, how could one ever leave the vicinity of an airport?
And the benefit of a power on approach is clear: you have much better control of the airplane.
Not sure I follow that Josh.
Sorry, should have been clearer – the initial part was two separate statements ie speed is more critical in a single as opposed to a twin, and separately more critical in a jet than piston.
There is a risk that rapid reduction of power can lead to a stuck valve in Lycoming engines.
Is there any difference if you reduce power at altitude to do a “glide” approach compared to reducing power when you start the flare?
There is a risk that rapid reduction of power can lead to a stuck valve in Lycoming engines.
Why is that? I don’t see the connection. The valves get stuck in the open position (if they get stuck in the closed position, you have a bigger problem because your pushrods go banana shape, their guides break, you lose all oil and your engine stops). This is because friction exceeds the strength of the two springs that pull the valve back. I happened to me at 65% BHP in cruise. Most of the time it happens for a brief time during startup, referred to as the “Lycoming morning sickness”.
The reason it happens is that there is burnt oil and deposits in the valve guide. Only way to fix the problem is to remove the valves and clean the guides. Then it won’t happen. Lycoming recommend doing that every 400h, I do it every 100h just to be safe…
Only way to fix the problem is to remove the valves and clean the guides
Lyco fixed that with chrome guides about 15 years ago. The newer cylinders are marked with a “C”.
Lyco fixed that with chrome guides about 15 years ago. The newer cylinders are marked with a “C”.
The SB still applies, only that it is recommended every 1000h instead of 400h. The way this engine is manufactured, there will always be crud between the valve and the guide. The new valve guides can also be installed in the older cylinders.
The service instruction for the new valve guides is here: http://www.caa.si/fileadmin/user_upload/pageuploads/AD-NOTE/AD-2006/093_sb_SI1485A.pdf
The SB for the test is here: http://www.caa.si/fileadmin/user_upload/pageuploads/AD-NOTE/AD-2006/093_sb_SB388C.pdf
Why is that? I don’t see the connection.
My understanding is, that this is the “reverse” of morning sickness, rapid cooling of different metal alloys (stem, guide) with different expansion rates.
Peter, where exactly is the “C” printed on the Cylinder?
The merits of the “wobble test” are debatable. Doing the test every 100 hours seems excessive and costly. Lycoming recommends frequent oil change as a mitigating strategy.
Shock cooling is also the theory behind the bent push rods, that happened to my colleague last year in a Piper Arrow (see story below). The culprit turned out to be a fuel servo issue, which led to rapid loss of power, which led to rapid cooling during the emergency descend, which likely led to a stuck valve, which led to bent push rods.
Not directly related, but interesting story from my colleague:
Seattle Center cleared me to the Ellensburg VOR and then RADDY intersection which is on the CHINS arrival. Just before arriving at ELN, she sent me off to Seattle Approach. Upon checking in however, Seattle Approach wanted to know if I was ready for an amended clearance. Responding with a quick “ready to copy”, they sent me back on Victor 2 and negotiated with me to go up to 10500. A mere 500 feet I thought was not too much to ask to get a fairly direct route home. This vector back to the airway will turn out to be the one act that likely saved us from being on the evening news.
As the Arrow sluggishly made its way up to 10500, I noticed that our ground speed had slowed to a mere 97kts from its usual number in the 125-130 range. Remembering the 11-13kts headwind I was expecting at this height, I thought perhaps we were just paying back the incredible tailwind we got in the morning. Winds aloft perhaps is conserved like other forms of energy right? But cross checking with the airspeed I noticed that we were not speeding back up after leveling off. Aha! It must be the richer mixture I used to do the climb, let me just tinker with the leaning again so we get the most from that trusty Lycoming.
Just as I was still thinking about the mixture, the engine tone made a sudden and abrupt change that was noticed by everyone in the plane. It was a low frequency shudder and thudding noise that resonated through the cabin. I took one look at my airspeed and noticed it was dropping as was my altitude. Fuel pump, on. Tanks, switched. Mags, left and right bank, both sounded just as rough. Prop speed, adjusted and made no difference. All the engine instrument indication from oil pressure, cylinder temperature, to fuel pressure all looked good too. At this point we have lost a full 500 feet and we had a decision to make. Do we continue on to cross the rest of the mountain pass which rises up or do we turn around and put it on the ground in the middle of the valley before things get rocky.
To be completely honest, a hint of get-home-itis did cross my mind for about a fraction of second. My mind conjured up the thought that we could ride out this rough sounding engine home so we do not have to put up with the inconvenience of figuring out how we will get home that night. Of course the years of reading stories of pilots who should have put their plane down earlier on before their disastrous end took hold of me and shook me saying “Are you crazy!! Land this bird now!”
A quick glance at my VFR map on my iPad that I always have open even during IFR flights revealed Cle Elum airport (S93) as a big inviting circle that our escape. Before my finger made the half inch movement onto the radio button, I banked the plane to head back east. “Seattle Approach, Arrow Nxxxx is experience engine roughness and we are going to divert to Cle Elum Airport, Sierra Nine Three. We would like to get vectors.” Without skipping a beat the controller gave me a heading of 070 and pointed me towards the airport. My eyes changed over to trying to spot the airport which was a lot harder than I thought. Initially I fixated on looking at what turned out to be the main road in the town. Another glance at the sectional and I finally spotted the words “Cle Elum” on a piece of tarmac and kept it on the left side so I always could keep it in sight. Thank goodness Seattle Approach did not decide to continue the CHINS arrival that Center was steering me towards (at my behest no less!), or we would have been looking for the flatting part of a forest to land in right now.
On the spiral down we attempted several times to see whether we could produce enough power to hold altitude. Each time I advanced the throttle up, I would get a louder sound of a sick engine probably telling me to stop torturing it. The protest of several backfires later, I decided not to negotiate for more thrust and accept what I had for the spiral down. There was plenty of energy left as we circled our way down to field elevation at 1944 ft. When we passed 8100ft, which was MVA for Seattle Approach in that area, the controller asked me whether I intended to continue IFR into S93 which had me puzzled. Cle Elum has an approach? Ah, he wants me to cancel IFR so he can continue helping me. No problem, the magical words were exchanged we were now under a new VFR relationship.
At about 6000ft or so, my calm sounding controller came on the radio to inform me of another piece of news. “Cle Elum is currently closed due to fire fighting. Are you declaring an emergency?” Another great tip from that morning popped into my head. Nobody has ever gotten into trouble by declaring an emergency when there is something actually going wrong and you are not buzzing the control tower. I confidently came back onto the radio, “Yes we are declaring an emergency, we are going to land at Cle Elum.” To which the controller responded with the phrase that I have only read or seen on Discovery Channel’s Mayday, “Nxxxx, how many souls are on board?”
A period of silence then came and went in the cockpit and on the radio. I was busy keeping us in a steady spiral down which seemed to take forever from 10000ft, and the controller as it turned out was in contact with the fire fighters on the ground who scrambled onto the runway to remove an orange X that was weighed down with rocks. Approach came back on the radio to let us know that we were about to go below his radar coverage, that there will be folks on the ground to meet us, and if we could give them a call once we are on the ground to let them know we are alright. “Nxxxx, frequency change approved.” Sounds good.
Engines do not typically quit when running with low power twds the end of the flight.
I was under the impression that this was one of the points at which they were most likely to quit…
Sudden changes in temperature, mixture, pitch & bank (if the tanks are on the low side you may get a cut during maneuvering). Movements of the throttle lever (an opportunity for linkages to break)… Carb icing at low throttle settings.
It does make sense to me that you’re more likely to have a problem whenever you make a change.
Engines quit when they’re idling sometimes, for various reasons summarized by saying that many of them aren’t designed to idle for long periods. That would lead one to think the gliding/idling approach to avoid issues with engine failure is a self fulfilling situation. However the most recent example of engine failure on final to my base was a Lancair making a flat, powered approach. He added power to make the runway, the engine quit and he hit the fence, flipped over, all on board killed.
I think a powered approach with a steady, low power setting might be the best situation for the engine. Try not to change power settings much until after you clear the fence.
The culprit turned out to be a fuel servo issue, which led to rapid loss of power, which led to rapid cooling during the emergency descend, which likely led to a stuck valve, which led to bent push rods.
That’s a great story, Lucius. Thanks for posting it.
What was the fuel servo issue? Was it icing?
engine failure on final to my base was a Lancair making a flat, powered approach. He added power to make the runway, the engine quit and he hit the fence, flipped over, all on board killed.
Which one was it? Was it a homebuilt, with a 80-90kt Vs?
