Engine Failure on Final

[Sunfish]

Quick question and please don't bite my head off just yet.

Now that I've got my constant speed and retractable endorsement, I'm flying the Tobago and the Arrow a little more.

Both of these aircraft glide like a brick, and reducing power on final can produce some pretty high rates of descent.

As a result power control is slightly more critical than a 172 , PA28,152 etc.

Now my question is, "what happens if you are at 500 feet on final, with gear out flaps out, and the engine quits?" I'm assuming that you are in a stablised approach at the required reference speed - say about 75 knots.

Now with full flap I'm not going to make the field in either aircraft. So do I raise flaps? Do I raise the gear (in the Arrow) in order to produce a better glide ratio?

One instructor I've worked with (ex military) encourages a slightly steeper approach path than others, which I guess leaves more room to glide if the engine quits.

Others want me to get a little low and on the back of the drag curve and then use a lot more power to bring the aircraft in, especially on short strips.

Can anyone advise me? Next sortie I'm thinking of going to the training area and setting up an approach at 3500 AGL and examining what happens.

We have drills for engine failure on takeoff and elsewhere, but I haven't noticed engine failure on final anywhere.

It may be that the geometry of certain strips is such that you can in theory glide the required distance, but I'm not sure if you could do it with flaps out.

[BEagle]

If you fly a light aeroplane like an airliner and drag it in on a 3 deg approach, you will undoubtedly land short.....

If you fly a glide approach, you should get in OK.

Between those 2 extremes it's your choice.

[A and C]

Remember on the PA28R the override will have to be pulled or the gear will stay down.

Most modern thinking seems to say that if you are going to crash do it with the gear down as so the thinking has it the gear will absorbe a lot of the energy.

Howerver IF it ever happens you will just have to call it as you see it ........... I guess that is what being the captain of an aircraft is all about.

[IO540]

The best range glide configuration is a clean aircraft i.e. no flaps, gear etc.

Whether this helps is another matter. If there are houses just before the runway but there is a field right below where the engine quit, it's obviously better to not try to reach the runway(which one won't anyway, from a 3 degree approach).

I don't think a TB10 or an Arrow are more of a "brick" than a PA28 or a Cessna. They just fly a bit faster :O

[Final 3 Greens]

Sunfish

If approaching a normal length runway, I would be very uncomfortable if I did not have enough energy in the airframe to glide in from 500ft, in the landing configuration.

You might wish to consider thinking about BEagle's advice and then work with an instructor to develop and practice a profile that you feel will get you into the field comfortably.

In an Arrow, I'd be looking to pass 500ft at less than 1 mile from the threshold.

Flying into short runway is a different matter, you need to weigh up the risks and decide whether they are worth taking.

This is similar to flying a light twin out of short strips, you may have to accept a short period in time where you passively accept a risk event could happen (and evaluate the severity) or avoid the risk by not going there.

[bookworm]

If you fly a light aeroplane like an airliner and drag it in on a 3 deg approach, you will undoubtedly land short.....

If you fly a glide approach, you should get in OK.

Between those 2 extremes it's your choice.

What really happens between those extremes? Say I have an aircraft with a 7 degree glide -- if I set up for a 6 degree approach and the engine quits, don't I end up going through the boundary fence just as if I'd set up a 3 degree approach?

The problem is therefore that either you have to fly every approach as a power-off glide, or you have to accept the risk of an off-airfield if the engine quits. I do wonder whether, for larger engines at least, the operating regime involving repeated glide approaches puts you at a greater risk of an engine failure overall.

[stiknruda]

Sunfish, if the engine really did quit, then pulling the prop pitch back into coarse (feathered) would also reduce drag considerably.

Stik

[Chilli Monster]

Not biting your head off - please don't take it that way.

There is no need to change your thinking from what you used to do before. PA28R and and the TB series (I fly a '20), once you've got gear and flap down, are no different to their fixed gear counterparts. They don't "Glide like a brick" (I fly both - I know).

If you were flying approaches before that would enable you to reach the runway if the engine quit - that needn't change.

What I would say is don't be in such a hurry to go full flap on final. Leave it until you know you can make the runway, in full drag configuration, if the engine quits. Then, and only then, should full flap be applied

[Say again s l o w l y]

More people end up in the accident reports for running off the runway than for losing the engine on short final. SO don't constantly push the limits of your a/c purely because you potentially could get a failure at low level.

Short of doing a glide approach each and every time, there is no sure way to protect yourself from an engine failure a too low an altitude to glide to the runway.

If you lose the engine at low level, don't start trying to reconfigure it, just do the best with what you have available.

Lifting and raising gear and flap, causes more drag than just leaving it extended. It's an emergency, so concentrate on the basics, fly the thing and try to get it down so that you at least have a chance of walking away.

If you keep control you always have a chance, if you lose it because you are trying to reconfigure, then you have none.

Stick's trick of pulling the pitch back to fully coarse can make a difference to your glide, but it depends on whether you have the ability to still affect a pitch change. Try it and you'll be pleasantly surprised. (Especially in something as "brick-like" as a TB 10)

[Final 3 Greens]

How about the ancient art of slipping, with power.

Increased drag, increased sink, good way to lose height quickly and can be removed instantly without causing ''in transit drag'' penalties.

[Zulu Alpha]

One thing I do regularly in our Arrow is practise engine out glide approaches. Put youself somewhere near the field and close the throttle at 2000 ft and try and make the runway. Even though I do it regularly its difficult as wind etc makes a big difference. I normally find that I am much better at the second attempt so its good to keep current.

As you say, the Arrow glides like a brick, particularly with full flaps. I therefore always stay high and wait until short final to add the last bit of flap.

I have tried removing the flap when practising glide approaches. I find that reducing from 30 to 20 degrees helps but any more hardly makes any difference, This is why I leave full flap to short final.
If you are on short final, have put in full flap and are low when the engine quits then I would leave the flaps as removing them is one more thing to distract you. This is why I always leave the final bit of flap to as late as possible.

As for the undercarriage I would just leave that down. At 90 kts it doesn't make a huge difference and you will have to hold the automatic retract override which ties up one hand at a busy time. It also takes 20 secs to cycle up and another 20 to come down

All the above would depend on the situation, If I was going to hit a house I might try everything to stretch the glide, however if it just meant landing in a field I'd probably concentrate on doing that well and without injury and let the insurance company take care of the aircraft. One danger with stretching a glide is stall/spin and that could be more serious than the engine failure.

Again, I recomend trying a couple of glide approaches regularly.

[djpil]

There's some good advice for you there, Sunfish, especially from Say again s l o w l y & Chilli Monster. As noted, with an engine failure, there's a good chance that you lost oil pressure some time before so don't worry too much about prop pitch.
but I haven't noticed engine failure on final anywhere You did glide approaches in your PPL training - unless you were close to the field/high enough when you closed the throttle you weren't going to make it.
Flying in the USA I got comfortable with the power off turning approaches in the Pitts (http://www.airbum.com/pireps/PirepPittsSuperStinker.html) - not legal in Australia.

[A and C]

At windmilling RPM the prop CSU is below it's controlling range and so the prop will be on its fine pitch stops.

The PA28R cant feather but on a twin you will need at least 1000 RPM to get the prop to move towards feather and to keep the feathering stops dis-engaged.

[foxmoth]

Lifting and raising gear and flap, causes more drag than just leaving it extended.

Agree with this as far as the gear goes - raising flap from full will reduce drag, but you will probably need to lower the nose for a slightly higher best glide speed, if you are low when this happens then you will probably lose as much doing this as you gain raising the flap - and if you hit the hedge you will then be going faster!:uhoh:
Trying the various options at height and seeing what happens is a good way to sort it - let us know what you find.

[Human Factor]

Not sure of the actual stats, but consider a risk assessment.

How often is your engine likely to fail at 500 feet on final?

Statistically, not often. That's not to say it won't ever happen, however the probability is not high in a (relatively) modern single. You have to balance this against the possibility of screwing up a landing having done an approach which is potentially too steep. You're increasing the probability of this by doing something other than the standard 3 or 4 degree powered approach, although once again, the probability itself is not that high.

At the end of the day, it's a balance of probabilities and you have to decide for yourself. From my own point of view, I'd work on the probability that the engine is likely to keep going. If there is a likelihood of it stopping (perhaps following rough running for example), which is likely to make itself apparent long before your approach, modify your plan accordingly.

[Say again s l o w l y]

How often do people lose the engine on final approach?
If you think about it logically, why is it more likely to die at that point than any other?

Most engines go pop when under load, on final approach there isn't a lot of load, so if you had no indications of problems before hand, why would it fail then? Apart from sod's law and carb icing.

Power changes usually cause issues as well as running at a high power setting for a prolonged period, but I've never seen any stats that show what regime of flight most failures happen in. It would be something I'd be very interested to see. Though I assume it to be in the cruise, since that is obviously where most engines spend their working life.

Going back to an earlier point.
If you retract flap, then you will lose lift and therefore height, use the K.I.S.S method for any emergency. i.e. don't start coming up with "cunning" plans when the doo-doo hits the fan, you'll only make it worse. Use the POH for procedures............ (repeat ad-nauseam)

[Chilli Monster]

Does sod's law include fuel mismanagement? If not then there's a possibility (and that HAS happened to people).

[Final 3 Greens]

standard 3 or 4 degree powered approach Standard, for multi engined airliners making ILS approaches.

[hugh flung_dung]

SAS:
"why might an engine fail on final?"
Well if the engine is at the back and you were to inadvertently pull mixture rather than carb heat :uhoh: ... Someone I know intimately did this many years ago in a Long-eze. They noticed when the aircraft started to sink and throttle didn't have any effect - fortunately the air brake is effective so by raising that the runway was made, engine restarted on the roll and nobody every knew about it (pssst, so keep it a secret :ok: )

"Lifting and raising gear and flap, causes more drag than just leaving it extended" - this may well be true for some larger types but I doubt if it's true for an Arrow. The gear and doors don't change their orientation compared to the airflow and nothing else pops out into the breeze during the process; so where would the extra drag come from? Raising the flaps certainly causes short term sink but there is a nett gain in glide angle provided the speed is OK so may well help things early in the approach - it also means you may be able to use them again to jump obstacles.

Stiknruda:
at idle the prop is on the fine pitch stop and is unlikely to respond to prop lever movements (although maybe an electric one would).


The over-riding message through all this should be to fly the aircraft at the correct speed and to make a decision about the options - not to keep pointing hopefully at a runway that you may not be able to reach. A controlled arrival in the best available place is very much preferable to an uncontrolled arrival at somewhere chosen by the gods of aerodynamics.

HFD

[Human Factor]

Standard, for multi engined airliners making ILS approaches.

Indeed it is. A 3 degree slope requires a rate of descent of approximately 5 x your groundspeed. ie. 130kts = 650 fpm or in light aircraft terms, 80kts = 400 fpm. A four degree slope will be a little more, approximately 6 x your groundspeed. ie. 80kts = 480 fpm.

If you're coming down short finals at significantly more than that in a light aircraft, you're more likely to over-flare and cause yourself a problem.

The one thing that connects airline flying and light aircraft flying:

A good landing comes from a stable approach.

The scale and the datums may be different but the principle remains.

[Final 3 Greens]

If you're coming down short finals at significantly more than that in a light aircraft, you're more likely to over-flare and cause yourself a problem.This is a very strong statement - I had typed nonsense, but edited that as it was rude.

Also, you haven't allowed for headwind in your approximation of the sink rate required.

In a PA28, you would be at 75kts, less a typical headwind of 10kts =65kts, so a 3 degree slope would require 325fpm, from a distance to the threshold of about 1 mile, which is not sensible in a light single, IMHO. The stronger the wind, the worse the numbers.

I would approach around -600 fpm, adjusting for wind accordingly, giving me a very comfortable and stable approach.

Having got my licence in 1994 and made several hundred (incident free) landings since, I speak from experience, not theory.

Having also operated a lot in a CATZ, there simply was not room to make a 3 degree approach, a 1/2 mile final from 300 feet was normal.

And it's not only light aircraft that can do this, have you experienced the 146/RJ on the 5.5 degree glideslop to LCY/EGLC?

There is another thread about bomber circuits - there is some fit with 3 degree approaches and these.

[High Wing Drifter]

Foxmoth says:
raising flap from full will reduce drag, but you will probably need to lower the nose for a slightly higher best glide speed
Agreed. For the Arrow, the best glide speed with 2/3rds flap is about 85kts and about 80ks with full flap, so a little nose lowering would be in order. FWIW, I noticed that there is virtually no sink when raising full flap to 2/3rds on the Arrow..or indeed any of the aircraft I've flown with flaps (with the possible exception of the AA5). I would not remove more than the last stage though!

Human Factors wrote:
If you're coming down short finals at significantly more than that in a light aircraft, you're more likely to over-flare and cause yourself a problem.
I agree with F3G. I don't believe that a steep approach is particuarly challenging. As mentioned before, a full flap glide approach in an Arrow feels more like a dive bombing exercise. Even a barndoor flap glide approach in a 152 is pretty steep. But is pretty much bread and butter flying...really...IMHO.

[Biggles_in_Oz]

After a long trip and then side-slipping-in on final due to strong cross-winds, the thought of fuel-starvation caused by unporting of an emptyish tank does cross my mind. :uhoh:
So, I tend to favour a dive-bomb the runway approach.

The Arrow gear doors make fantastic airbrakes :yuk:, but because of the gear cycle-time I'd leave the wheels where they are if you're below about 700'