SEIFR Minima

[Krallu]

Hi guys!

Talking about single engine IFR flights. What are you guys's personal minimas? Worst weather you fly SEIFR in?

Would like to hear some different minimas here to see where the rest of you guys place yourself when it comes to flying SEIFR flights.

MEIFR then you have double security with 2 engines then you can fly to minima. But now talking about SEIFR.

Thx a lot!

[OzExpat]

Excuse me? I'm probably missing something here but, for the life of me I can't figure out what it is! I'm not sure what you're getting at. There are rules, in many countries, especially involving destinations that have an ATC unit.

Are you considering the possibility of engine failure when the wx is at or above the minima for your approach? I have to ask... why?

What are you going to do in the event of an engine failure?

There aren't any choices, so you do what comes naturally... crap yourself, kiss your ass goodbye and hope for the best.

Am I missing something here?

[Krallu]

Ehh, not sure about what you are trying to say.

Lets say the regulations say 200 ft DH. But as a responisble pilot you don't go flying SE IFR to 200ft. You develope your own personal minima for lets say perhaps 800ft where you at least have some VMC below the clouds in case of engine failure.

I am interested to hear what personal minimas you people have? Or are you all flying to regulation minima with SE?

:rolleyes:

[OzExpat]

I'm still puzzled. If I try to look at the scenario you're suggesting, it seems that a SEIFR is conducting an ILS in IMC and, at some point in the approach the engine fails. Is that about the size of it?

In that case, why not consider the engine failure as you pass the FAP?

See, no matter WHERE the engine failure occurs, there's not much you can do about it because the aeroplane is going to go down. And it'll go down much more steeply than you're nice comfy 3-degree ILS path. So it's like I said yesterday...

There aren't any choices, so you do what comes naturally... crap yourself, kiss your ass goodbye and hope for the best.

Not that I actually fly SEIFR these days... I've had enough problems with engine failures in singles, earlier in my career, even in good weather, to see the folly of SEIFR. However, in those days, I would ALWAYS fly the approach to the DA/MDA, unless getting visual higher up.

You might find it useful to check out topo charts in advance, to get an idea of your chances of surviving your scenario. There are, of course, many places around the world where it's actually better NOT to know what you're going to hit in the event of an engine failure!:eek:

[Krallu]

Hi again!

Yes, I agree that the same will happen if you get an engine failure at 200 ft or 800 ft. But if you have a personal minima not to fly with cloudbase lower than 800 ft you have at least VMC weather to chose a field to land on after you pass 800 ft.

Or when flying en-route you encounter an engine failure and then you have at least some time when reaching 800 ft to choose a place to land. Compared to 200ft cloudbase. So then 800 ft cloudbase must be more safe to fly in than 200 ft when it comes to engine failure?

You are saying that you are flying with minima weather even with SEIFR??

[unfazed]

Krallu

If you maintain 1,000 feet above the highest obstacle within 5nm of your track then in the London area your MSA is approx 1750amsl

So a pragmatic and sensible personal SE cloud limit might be 1000 foot agl, this will provide some level of VFR in the last couple of minutes for finding a landing field. Unfortunately you may still hit a tall mast during descent whilst IMC unless you know where you are in relation to the masts.:ok:

Must emphasise that this is a suggested personal limit based on a specific area, if near high ground then you might need to wait for 500 ceiling (or higher) above high ground prior to flight (i.e. ensuring no cloud on hills).

Most mountain training recommends 2000 clearance above the ridges of high ground if wind is in excess of 20Knots so it is not just about clouds but also turbulence.

[Tarq57]

Or when flying en-route you encounter an engine failure and then you have at least some time when reaching 800 ft to choose a place to land. Compared to 200ft cloudbase. So then 800 ft cloudbase must be more safe to fly in than 200 ft when it comes to engine failure?
That works.
Provided the terrain elevation stays at zero, or at least, well below 800'. And you know the cloud isn't lower anywhere en-route.:E

[FlyingForFun]

If you have more restrictive minima for SE IMC for safety reasons, then do you also refuse to fly SE at night (when you probably have even less time to see what you're about to hit before you hit it)?

I can see why it might be desirable to have more conservative minima, and some pilots apply the same conservatism to all flight.

But there are lots of pilots who insist on having cloudbase 1000' agl for a whole route (in which case it is rare that you'll be able to use your rating for a flight which you wouldn't have been able to do without the rating) but then quite happily fly SE at night. Or vice versa. Neither of which seems entirely logical.

FFF
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[IO540]

I rarely fly at night and would not fly over really dark terrain unless I was close to home anyway.

Flight over cloud whose base is say OVC005 is not good either.

But everything is a risk and whether you get it depends on how often you expose yourself to it. One should always have an escape route and flying at night means you don't have one. Likewise over water without a life raft (lots and lots of people, including flying school sponsored fly-outs, do that).

But with the escape route covered (e.g. carrying a raft) I don't see a problem.

Just my view.

[OzExpat]

Okay, I understand what you're saying now. If you're going to impose some sort of higher DA/MDA on yourself, to allow you an opportunity to have some control over the descent in an engine failure situation, that's not a bad idea.

It might, however, limit your options for destination and/or alternates. This is especially true for selection of alternate aerodromes and your "personal minima" could well result in the need to use an alternate aerodrome that is quite a long way away from your intended destination. All that extra flying, using one engine that has as much ability to fail enroute in that situation as in an approach scenario. Will you then apply the same personal minima to your enroute flying?

This could mean that you're going to be very limited as to when and where you fly because the weather won't always be as cooperative as your personal minima demands it to be.

To answer your other question... yes, when I flew SEIFR all those years ago (and was young, stupid and bullet-proof :uhoh: ), I was always prepared to go down to my legal minima as per the chart, adjusted for PEC and QNH - I was never in a situation where temperature was low enough to adversely affect altimeter indications. Thinking back on those days, there was probably only a handful of times when I needed the charted minima - most times, I'd get visual a couple hundred feet higher.

And the engine never even looked like failing on me whenever I was in IMC. It did, however, fail on me in VMC once or twice during my career. Significantly, those incidents occured greater than 1500 FT AGL.

[englishal]

My SEIR minima is printed on the approach plate ;) If I have to go down to it I would.

However, I probably wouldn't set off on a flight knowing that the other end is at minima, unless it is forecast to improve.

I try not to think about SE engine failure too much. I have flown over the mountains of california at night in a SEP, and it didn't really worry me too much as the engine kept running. However I am a bit older and wiser now and probably would think twice about it now.

New GPS technology and accuracy can help in the even of an engine failure in IMC / Night...

[Julian]

I am same as EA, if the approach plate says 297' then thats my minima, if its 400' then thats my minima.

Wether I am flying SE or ME does not affect my minima.

[Wrong Stuff]

A discussion of the dangers of SEP IFR flying which concentrates on engine failure totally misses the true areas of risk in IFR flying.

Analyses vary, but typically mechanical failure accounts for less than 15% of fatal IFR accidents. Of those, about half of them will be vacuum and electric system failures, a quarter fuel exhaustion and a quarter mechanical engine failures. These proportions are roughly the same for both twins and singles. In the last analysis I read (Collins - Flying IFR) singles came out slightly more dangerous than twins for system failures, but significantly safer than piston twins for engine failures, even after adjusting for the higher proportion of twins flying IFR.

Krallu - if you're actually interested in evaluating and reducing the real risks involved in SEP IFR flying, I suggest you read a good analysis of the accident report statistics. Richard Collins has covered the question a number of times in his Flying magazine column. Alternatively there's a chapter in his book Flying IFR on the risks involved. The NTSB also publishes accident statistics - I believe they're at http://www.ntsb.gov/Aviation/Stats.htm but the site is down at the moment.

[funfly]

I think the guy has asked a valid question based on personal ability rather than flight safety.
I have found with my own VFR flying that having specific personal minima on cloud base, visibility and cross wind component has removed the 'shall I or shall I not fly today' dilemma. If it's outside of my personal minima I don't fly and if it is in then I do. These minima are based on my own comfort zone rather than the official figures for VMC.

[IO540]

mechanical failure accounts for less than 15% of fatal IFR accidents. Of those, about half of them will be vacuum and electric system failures, a quarter fuel exhaustion and a quarter mechanical engine failures

So, 1/4 of 15% i.e. 4% of fatal IFR accidents is engine failure.

That's not bad - I am not planning to run out of juice, an electrical failure is covered by having a vacuum horizon and a decent handheld GPS plus a handheld radio, a vac failure is covered by having an electric horizon+TC (plus staying awake). All these are arguably pilot errors - running out of juice definitely is.

So the risks due to engine failure are very low.
-

[FlyingForFun]

Funfly,
I think the guy has asked a valid question based on personal ability rather than flight safety
I don't think that's what Krallu was asking. I think he was specifically asking about flight safety. If it was personal ability he was talking about, then it would make no difference whether the flight was single-engine or multi-engine, but he has specifically asked about single-engine where there is an additional flight safety factor to consider. He also said himself:
You develope your own personal minima for lets say perhaps 800ft where you at least have some VMC below the clouds in case of engine failure.

Englishal has made a good point, though, which is worth emphasising. Personal ability should dictate in-flight minima ("I am out of practice, so I will use a higher DA than that published"), and if weather worse than these minima should occur, then a diversion must be made.

But if we are talking about flight safety in a single, then the minima we are talking about are planning minima. You should not set off if the forecast weather is below whatever planning minima you set yourself - but that doesn't mean that if you encouter weather worse than this, you need to turn back.

For example, you may set yourself a DA of 600' agl for an ILS (slightly higher than the published DA, because you are out of practice). But you might also set yourself a single-engine minimum cloud-base of 1000' agl for the entire route. That doesn't mean that if you reach your destination and the cloudbase is 800', you need to divert. On the contrary, the safest course of action is to continue the approach until you become visual, which hopefully will be just before your DA, then land. If you were to make the misguided decision to divert when the weather is below your planning minima but above your in-flight minima, all you are doing is subjecting yourself to further flying time with a low cloud base when have an increased risk of a bad outcome if the engine should fail. That is a counter-productive use of these minima. (Before everyone shouts at me, I'll add that a go-around must be carried out if not visual by your self-imposed DA, possibly followed by a diversion, but for the purpose of my argument I'm assuming that's not going to be the case.)

FFF
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[Keef]

I'm not sure exactly what Krallu's asking.

A. Would I fly if the cloudbase were below MSA/SSA but above DH where I'm going? Yes, provided I were in current practice. I've had engine "failure" too - in a single - and survived to tell the tale. I don't think cloudbase of 800 feet or 400 feet would make a lot of difference in the case of total engine failure - I'd be coming down at such a rate that it would be "what options have I up to 30 degrees either side of the nose?" in either case.

B. What DH minima do I apply? If I'm in current practice, the ones printed on the plates. Right now, not having flown an ILS for three months, I'd add a couple of hundred feet - but then, if the needles were bang in the middle, I'd cut myself a bit of slack on that.

By the way: minima is the plural of minimum. There's no such word as minimas (unless you meant to say "minimumses").

[bookworm]

mechanical failure accounts for less than 15% of fatal IFR accidents. Of those, about half of them will be vacuum and electric system failures, a quarter fuel exhaustion and a quarter mechanical engine failures

So, 1/4 of 15% i.e. 4% of fatal IFR accidents is engine failure.

I'm not sure that's the whole story. Bear in mind that these are flight under IFR, including those in CAVOK conditions. If you look at flights with, for example, ceilings less than 500 ft or visibilities less than 1 mile, they might tell a different story.

I recall, while I was flying SE IFR regularly, checking out the NTSB site to find engine-failure-related fatal accidents to prove just how safe SE over low ceilings and poor visibilities is. I stopped after finding an uncomfortable number.

I don't believe that SE over low ceilings and poor visibilities is an unacceptable risk, particularly with dual vacuum and dual electrics as some singles have. But I do think it's an increased risk, nontheless.

[IO540]

I agree entirely, bookworm.

Let me make 2 points:

It is just about impossible to always have an escape route. Well, one could depart, circle overhead, and then land, and that's about the only way. Or perhaps fly between two runways over totally clean open countryside.

In reality there are moments, on just about every flight, when an engine failure would be fatal. They may be only a few seconds, and are usually pretty obvious (you look down and all you see is houses) and the chance of an engine failure during those few seconds is so tiny it's never actually happened. But the more time one spends doing stuff like that (e.g. flying over water without a life raft) the more likely it is to happen.

The other one is personal minima. I think this comes from the countless CAA handouts on "good airmanship". What are my personal minima? I haven't got a clue. If a plate says 550ft MDA then I will fly it down to 550ft; land if visual. Why increase it to 1000ft or whatever, when it's obvious from the instrument indications (like the LOC rapidly heading for one end of the scale :) ) that it is going badly. Why can't pilots be trained to fly the approach as it is drawn, and give up on it if it isn't going correctly?

[bookworm]

It is just about impossible to always have an escape route.

After I had been flying SE IFR for about 3 years, we bought a handheld GPS. Flying at typical European airways levels (e.g. 90 or 100), with the assistance of GPS there is actually a reasonable prospect of gliding to an airport with lights and a decent runway for much of a typical IFR flight -- well typical for me at least: if you must go to Greek islands... ;).

[Fuji Abound]

I don’t think Krallu is concerned with approach minima. I think he is asking us for our opinion on what en route cloud base we would be comfortable with for SE ops.

Clearly there are those who will accept any en route cloud base presumably on the basis the risk of an engine failure is acceptably small. Then there are those who will apply an en route minima on the basis that in the event of an engine failure with their selected minima they feel they have a reasonable chance of setting up for a forced landing. If you consider the second group Krallu may be interested in what minima we feel would give a realistic possibility of setting up for a FL in a reasonably controlled way form cloud break.

[Wrong Stuff]

So, 1/4 of 15% i.e. 4% of fatal IFR accidents is engine failure.
I'm not sure that's the whole story. Bear in mind that these are flight under IFR, including those in CAVOK conditions. If you look at flights with, for example, ceilings less than 500 ft or visibilities less than 1 mile, they might tell a different story.

I recall, while I was flying SE IFR regularly, checking out the NTSB site to find engine-failure-related fatal accidents to prove just how safe SE over low ceilings and poor visibilities is. I stopped after finding an uncomfortable number.
Bookworm, that's a fair point, but I can't quite see where you're getting the doom-and-gloom numbers from.

I've had a quick look at the raw data figures that the NTSB provide on their website for 98, 99 and 2000 (shame they don't provide more, really). The engine failure numbers there look pretty much in line with the rough numbers I quoted from Richard Collins's book.

Of the 70 single-engine IFR fatal accidents, 5 have a first occurrence cause of engine failure for mechanical reasons, 2 for fuel exhaustion and a further one for undetermined reasons. Of the 5, one had a contributing factor of failure to perform an engine overhaul and a second was an inadvertent stall attempting to clear trees on a go-around with a perforated piston, so I'm not sure that should be included either. That leaves us with 3 or 4 fatal accidents with the primary cause of engine failure - which is within spitting distance of the 4% quoted earlier.

It is interesting though that the raw data generally includes the actual weather conditions at the time. Including all the loss of engine power IFR accidents, 8 were in IMC, 2 were unknown and 51 were in VMC. This is almost exactly the same IMC/VMC proportion as the twin engine failure accidents (5 IMC, 25 VMC - fewer accidents, but more often fatal), implying that the single engine aircraft data isn't skewed because they make up a greater proportion in soft IFR than hard IFR. This was also the finding of an analysis Flyer magazine undertook, where they found the proportion of singles remained around one-third of the IFR piston engined aircraft both on good and bad weather days.

So, provided you don't particularly avoid flying in good weather and hunt out the bad, it would appear the original statistics are reasonably accurate. Bear in mind there's a lot of data, so this is only a rough analysis. Also bear in mind that, being a SEP IFR frequent flier, I'm biased and that may be reflected in my analysis. I'd be happy to have any errors pointed out.

[S-Works]

Bah.

My mimima is the same IFR single or twin. if the donkey quits in IMC it does not matter if you have 200ft or a 1000ft you are going in and either you survive or dont......

I do have to say flying to Menorca this weekend IFR in the twin did make me "feel" like I would have longer for a mayday before the crash into the pyanees......:rolleyes:

[Wrong Stuff]

Just before deleting the downloaded NTSB data off my hard drive, I just thought I'd run one more quick analysis for my own interest. I noticed yesterday that none of the fatal mechanical engine failures happened in IMC, so I was wondering if you looked only at the IMC forced landings (including both mechanical engine failure and fuel exhaustion) what the outcomes were. Of course, this doesn't tell you the degree of IMC-ness (ie cloud base & visibility) but I thought it might prove interesting anyway.

For the 7 forced landings the worst reported injury percentages came out as:

Fatal - 14%
Serious - 14%
Minor - 29%
None - 43%

Of course, that's only for 7 data points, so treat it with caution.

What's obvious, though, trawling through all that accident data, is that spontaneous engine failure is a relatively unlikely way to kill yourself, and it doesn't seem to matter very much whether you're in a twin or a single. Most of the time people just seem to make a bad decision, fly badly and hit stuff really hard.

[IO540]

To me, the most telling thing is that there are just 7 data points, among the vast amount of GA activity going on in the USA.

Most pilots would die of old age before getting this situation - that's assuming they could fly 24 hours a day for the rest of their lives.

Same applies to a mid-air (except possibly at Stapleford on a sunny Sunday ;) )

[Krallu]

Wow what an interesting thread my question turned into. :)

Very interesting to see all of your ideas and suggstions.

Well, I think my question was more into the enroute cloudbase for a chance to spot a field before hitting something in case of emergency landing. For the approach you of course use the plate minima if you have to. But the planning minima could be higher if you arent comfortable flying a 200 ft approach or for safety reasons??

So, what do you guys use for enroute planning minima? And/or approach planning minima?

[IO540]

Depends if going VFR or IFR, and whether the VMC-on-top option is available.

It's really easy to get a list of TAFs, and METARs before going, for every flight, along the route, so why not? You get an idea of the cloudbase, and also the forecast should indicate bad weather like TS or TSRA, CB, etc. Every pilot should do this, for a selection of airfields along the route. I do this even for flights at airway MEAs e.g. FL150. Of course one has to look at other sources for enroute weather but that wasn't what you asked about.

This will also give you an idea of the cloudbase en route.

It's rare to fly a route of any length with it being OVC002 all the way along underneath. Obviously one could not do this VFR with a UK PPL - well some people will always try flying under OVC002 :ugh: It's an IFR or VMC-on-top issue really.

I think that overflying a 30nm area on which fog or very low cloud is forecast is OK. It amounts to an exposure lasting only minutes.

Overflying the Alps if covered in solid cloud is something else. There you have a 1hr or so exposure, with your only escape route being high enough, and having a GPS running a decent topo map so you can glide into a valley. The valley is unlikely to have cloud all the way to the bottom. I don't think I would do a flight like that again though ;) It should be SCT or better, and a satellite pic is a good way to check that.

Approach planning minima is what is says on the plate!