I've just been reading an accident report from the Summer 2013 issue of Flyer Magazine, and I'm left speechless.
It involves an engine failure on an SR22.
The report indicates that at about 11:22 the oil pressure annunciator light came on.
It then says that as the oil pressure continued to slowly drop, the pilot became increasingly concerned. (Pretty understandably!)
This is the first bit that got me......At 14:04 the engine failed!
That's 2 hours and 42 minutes after the oil pressure light came on the pilot was still flying!
The second bit that made my jaw drop was the bit which said "The pilot reported that the oil pressure indication dropped very gradually giving a false sense of security".
The third bit that got me was that the pilot reported that they normally maintained the oil level between 5 & 5 1/2 quarts. However the POH recommended that the aircraft should not be operated with less than 6 quarts, and 7 is recommended for an extended flight.
I don't want to suggest that I'm in fallible or anything; I've certainly made my fair share of mistakes. But I really can't understand anyone getting a low oil pressure light and continuing to fly for almost 3 hours. An SR22 is not a slow machine. It probably covered around 400nm in that time so there must have been plenty of landing opportunities.
Has anyone seen the official AAIB report for this incident? I'd love to read it to see if there was some pressing reason for not landing when the oil light came on. The only one I can think of would be a very long sea crossing. But that doesn't seem to be the case here, as when the aircraft did come down, it was over land. There is no indication in the magazine which agency did the report, or in which country it happened.
Am I the only one surprised about this? I'm left speechless.....
Colm
Here you go... ATSB Engine failure involving a Cirrus SR22
The third bit that got me was that the pilot reported that they normally maintained the oil level between 5 & 5 1/2 quarts. However the POH recommended that the aircraft should not be operated with less than 6 quarts, and 7 is recommended for an extended flight.
You have to put this into context. Often, the POH recommendations about the oil level don't work for a given airplane. The way the oil pan capacity is determined is very simple: there is a maximum allowed oil consumption per hour (given by the engine maker) and there is is a given maximum fuel on board, i.e. endurance. Now the oil pan has to hold enough oil so that for the longest flight possible and the highest oil consumption possible, there is still twice as much oil in the oil pan as required for the lubrication to work.
If I put anything remotely close to the recommended oil level in my aircraft, it will all be thrown overboard in the first 30 minutes through the crankcase breather tube and I have to scrub it off the belly. Also as owner of an aircraft, one is intimately familiar with the oil consumption of the engine and if it's anywhere near those certification limits, then the engine needs serious attention.
Continuing for hours with an oil warning light on is plain stupid. Having a different oil level than recommended by the POH can be reasonable.
Reading the report further, it looks like the opposite case was true: the oil consumption was exceptionally high. Well, that is easy to see on the dipstick and if it's not a rental aircraft one sees for the first time, it's clear that something is wrong and action needs to be taken.
The trick for finding original documents when somebody has quoted a phrase from it but (often for some bizzare reason) not supplied the reference is to google on a fairly unusual phrase, in double quotes, e.g.
"The pilot reported that the oil pressure indication dropped very gradually giving a false sense of security"
You get 3 hits, all relevant, of which one is the report.
Another thing which is staggering in the full report is
"The average oil consumption for the combined accident and previous flight was about 0.5 quarts per hour which is near the upper end of the maximum oil consumption for the engine"
1 qt of oil every 2hrs is HIGH. I don't know the airworthiness limit for the Conti IO550 (Lyco IO540 is 1qt per hr) but questions should have been asked a little earlier. Even if one looks at it purely practically, that much oil burn reduces the endurance of the aircraft to that of a C150.
But this is just a combination of a "non technically interested" pilot and an inept maintenance company, which is probably common. Imagine a "non technically interested" pilot getting his plane serviced at the "maintenance" company which installed my TCAS, for example.
Having a different oil level than recommended by the POH can be reasonable.
Normally you need a lot more oil in these engines before it disappears straight out. On the IO540-C4 you need to put in 10 quarts before that starts to happen. The certificated oil sump capacity is 12 and the minimum level in the POH is 6. The POH says "fill to 9" unless doing a long flight and then fill to 12 and that is reasonable if your oil burn is very high. But obviously the actual oil burn overrides this and if you are burning 0.5qts per hr then you can't do any long flights at all and be within the limits.
What are the certificated limits for the SR22 engine?
The report says the POH recommends
The engine should not be operated with less than six quarts of oil. Seven quarts (dipstick indication) is recommended for extended flights.
6-7qts are very narrow limits within which to work. It's OK with an engine which burns 1qt every 5-10hrs (which is more normal). But compare this with the Lyco limits of 6-12.
I had persistent oil pressure indication problems on my plane. Eventually I had a backup gauge installed, because a low oil pressure indication means "brown trousers"....
OK, I'll fess up with what I did in the hope that someone else might benefit...
In a different galaxy a long time ago, the oil pressure annunciator came on shortly after departure. Actually, it flickered with increasing brightness to full on in about 30 secs. During this time, the oil pressure guage remained exactly where it had been in the last 20 hours flying, the oil temperature remained completely normal and there were no other signs of mis-behaviour, smells, power loss, etc.. The excellent engine, flown extensively by me, had very low oil consumption and correct oil level before take off.
On this basis I deduced sensor failure and elected to continue the flight. WRONG!!!
The Cessna POH is unhelpful on the subject, considering only 'loss of oil pressure' and not conflicting indications, and maintenance authorised me to continue flying to my ultimate destination where a spare would be waiting. What neither of these sources apparently considered is that there is an AD on some of these sensors, which are mounted on top of the engine, regarding loss of oil through the sensor. See here. They cite a risk of total oil loss through a cracked diagraphm and a risk of engine fire due to oil cascading down the sides.
My flight continued normally however and after a second (maintenance approved) flight the sensor was removed to reveal a small amount of oil partly submerging the microswitch and nothing else. However, my decision to continue was clearly gung-ho and the next time I see any kind of oil pressure problem I will land as soon as practicable, at least to determine if there is any risk of oil loss occurring.
[URL fixed]
To know how much oil your engine need is for mee the most important. 1qt per 10h are the average. When I do traffik patterns I need a 1/2qt extra for the hard work. I have always a littel to high oli pressure indication would this drop only a littel, I land an let it checked!
That's 2 hours and 42 minutes after the oil pressure light came on the pilot was still flying!
That gives you a feel for just how BIG and EMPTY Australia is....
That gives you a feel for just how BIG and EMPTY Australia is....
It is, but on that particular route there are quite a few places to set down. In addition, pretty much any cattle or sheep station in the Outback has a landing strip. What IS tricky out there is to obtain maintenance (ask me how I know.....), which may well be what prompted the guy to carry on.
This theme is more clearly (though still not well) covered in helicopter flight manuals, where the pilot might read the phrases "land immediately", "land as soon as practical" or "land at a suitable location for maintenance". Though they seem clear, there is still room for a problem, and I have discussed this with the regulator.
The latter two allow the pilot some judgement, and are obviously based on a perception that some time is available for "safe" operation of the aircraft, before things get worse. You just might be eating into the longevity of something. There is not usually a unit of time associated with these.
However, I have argued that the "land immediately" is misleading and deceptive, and can defeat it's own intent. If you are stating "land immediately", what you really should be saying to the pilot is to "crash immediately", which means that the whole aircraft is to be sacrificed, and the risk occupants is less in a crash, than an attempt at continued flight. The use of the term "land" to a pilot implies that the pilot should still look for a "place" at which a "landing" can be conducted, and this might not be immediate. The Cougar Helicopters S-92 crash is such a situation, and there have been others.
This theme was the subject of cockpit discussion, when during my helicopter training, while hovering in a confined area, 2 miles form base, the instructor simulated an alternator failure warning light (just by pushing the push to test). I picked up out of the area, and started to fly directly back to the base airport. "What are you doing?" he asked me... "Taking it back to get it fixed" I replied. "No, you're supposed to land in that area." I explained that it would not occur to me to land into an area when no maintenance was available for an alternator failure, when I knew that I could fly two mile to the maintenance base for repair, with no difficulty whatever. Apparently, that was not the purpose of the exercise, so the next time, he simulated a Transmission oil pressure warning, I landed in the confined area and shutdown, and I then had got it right.
Certainly the system failures on GA aircraft are generally much less life threatening than some helicopter failures could be, and at the risk of an engine failure, you can look for either a place to "land" or better, a place where when you land, you can get it fixed. These are judgements which a pilot has to make, and there are many factors to consider - hopefully the pilot is either familiar with most of them, of can get good advice in flight. I have certainly called for such advice during flight.
The time of continued flight in the case presented does sound overly long, but you'd be surprised how long an engine will run on very little oil, if you're prepared to risk a failure. In most cases, if I knew the engine and plane well, I'd be using some engine run time, to make a very gentle climb (so as to not overheat) more toward an area of choosing for my [possibly forced] landing, and monitor things very carefully.
During an engine breaking flight in a Cessna 206 I made the foolish mistake of going on a cross country scenic flight quite some way away. My only accidentally wise mitigation of risk was to fly very high, as it was a turbo. When, at 13,000 feet on a perfect day, oil started flowing onto the windshield, I knew that I had a problem, and was 39 miles from home, with nowhere better in between. There were no indications of a problem, other than a stream of oil, but that is pretty clear... I did not want to wreck a brand new engine, nor the plane. The engine was still running nicely, with no indication of an impending failure. I reduced the power to idle, and pointed toward home. With the help of a nice tailwind, I made a very nice forced landing at home, neatly on the runway, without ever increasing power from idle. I could have if I need to do so to save the plane, but this was dumb luck un-necessary. Yes, the plane was covered in oil - the filler cap had come off. Aside from a mess for me to clean, no harm done.
Yesterday I was test flying an amphibious C 182 (not the expensive one I have describe to a few of you! Different project). As I slowed on the step during my second water landing, I heard a loud "pop", and saw the glare shield in front of me buckle and return. It was a nice landing, on a calm lake, but did this plane have an engine mount defect I did not know about!? I was on the step, I could stay on the water, or get airborne, and fly the two miles to the airport. I had chosen the lake closest to the airport, but it would still be a misery, if a repair had to be affected on a floating plane. I added power and watched carefully, noting any change. Nothing was untoward, so I took off, and flew it home (even remembering to lower the wheels, while distracted!). The plane had a loose "V brace" so this "oil canning" though highly undesirable, was not an indication of impending doom. My snap decision, with incomplete information had been the better one. At least a mechanic did not have to travel to meed me somewhere at someone's unfamiliar dock to have a look at the plane, while the water conditions worsened, so I had to pound the plane to get it out of the lake later....
These are judgement calls. Based upon pilot experience, some we get right, some we get not so right. This is one of the things which should be trained better, with examples. Hopefully, new pilots reading these posts can take away some wisdom, which will make them more able to cope.
It is, but on that particular route there are quite a few places to set down. In addition, pretty much any cattle or sheep station in the Outback has a landing strip.
Not much of the route would qualify as "station country" where I come from (the bush in WA) but maybe have different terminology in the East....but point taken...there were no doubt many landing strips along the way
