Glide approaches

[18greens]

In the old days they used to do glide approaches all of the time presumably due to the unreliability of engines. Gliders still do glide approaches.

Then we started doing powered approaches, presumably because the airlines need to do powered approaches (on the back of the drag curve) and instrument approaches demand the 3 degree thing.

When did the switch happen in the PPL teaching world?

[Pilot DAR]

When things reversed, and engines became more reliable than instructor skills.....

[Tony Hirst]

18G,

I read about these in Alex Kimble's book "Think Like a Bird", even in the 50's it seems to be regarded as the old way of doing things. Other than good practice, I don't think I really understand the logic. If anything the engine is less likely to fail at a low power setting during final when compared to any other part of the circuit (carb ice discussions to one side for the moment, that is down to equipment and technique).

Are you suggesting that an aircraft should be in glide range of the runway from any point in the circuit? If so I don't suppose that would be very practical for many airfields. with all the traffic and noice restrictions we have.

[18greens]

Tony,
I guess I am lazy, I fly a tight tight circuit and if i'm on my own and theres no one ahead then i'll chop the thottle and glide from abeam the downwind numbers, delighting from the joy of kissing the numbers and taxiing off at exit 1. It saves time, its quieter and you get loads of circuits per hour (and being constantly s*** scared of the inevitable engine failure I take every chance I can to practise glide approaches). And other than noise abatement why should we land any other way?

If the guy ahead goes so far out I feel uncomfortable I'll cut in (politely) or more likely go around.

Being in glide range of the airfield (or a good alternative) at all times makes me feel better. I'm not sure whether that affects glide or powered approach argument.

Pilot DAR,

I think you may have nailed the argument. However its just as hard to teach a 2 mile final with power as it is to teach a glide approach.

[llanfairpg]

The change started with the replacement of the Tiger Moth as the school training aircraft.

I know one CFI who still teaches and insists on glide approaches on all normal circuits

[Sir George Cayley]

I was taught glide approaches in the 1970's by ex RAF instructors. Our trusty mounts were Cessna 150s in which one could select 40 degrees of flap and dive near vertically but never exceed 80 mph.

Great fun, and it imbued me with a lifelong aversion to the 'modern' cross country circuit and powered approach.

I once read a book (wriiten many years ago) in which it was suggested that gentlemen should never "motor in". As a result I never have:ok:

Except when piloting things that glide like a brick:eek:

Sir George Cayley

[tigerbatics]

I think it was later than that. Glide approaches were taught to me as being the norm in the 1970's. Still the best way; with power for those who can't judge it properly, as I was taught, or who wish to land very short.

At some point the training reversed to make power the norm. Hence the daft size circuits. Perhaps it was after the CAA, with their fine minds, made a CPL a requirement for instructing. Then students had to pretend they were flying the airliner the instructor probably thought he ought to be flying.

The owner of what was the finest flying club in the world used to say that the three most useless things in a light aircraft were, a step ladder a stiff broom and a commercial pilot. I make no comment about that.

[kiwi chick]

I too, do what 18greens does. I always glide approach if there's nobody else around, or if there's nobody in front of me - for two reasons.

1) I like to get the practice - having past experience with an engine failure at 200ft AGL you can never, EVER be too practised. EVER!

2) I'm lazy at the end of a long working day. I can't be assed flying big circuits and spending five more minutes on finals when it's not necessary.

And I always call "glide approach".

:ok:

[Mark1234]

Personally I prefer glide approaches, but then I'm a glider pilot ;)

Seriously - having picked up power also, I'm generally uncomfortable with the 'what happens if the donkey coughs' factor on a powered approach, but I'm lead to believe that it's better for the engine - particularly doing circuits, glide approaches = shock cooling, and bad for the cylinder heads.

[RatherBeFlying]

My preference is for glide approaches, but when it gets cold, the engine needs to be kept warm, especially for a touch and go.

So in cold weather, more flap or sideslip to counter the extra revs.

[18greens]

I note with interest the requirement to call glide approaches. Surely the only requirement is to establish circuit priority (unless local rules require glide approaches to be called.)

When does an approach become a glide approach. I've never seen anything written down about what is a normal circuit (how far out, when to turn etc) with exception of the noise abatement approaches. Theres no requirement to call extra wide circuits.

A glide approach in a motor glider could be flatter than a powered approach in a cessna and a powered approach in a pitts will be steeper than a glide in a cessna. What's the reason to call a glide approach?

The comment about shock cooling is noted.

[gasax]

I must admit that calling a glide approach is a new one on me. If there is a particular circuit size or routing that is what you fly. (I've been based at strips for the last 20 years and so have a near religious observance of these things). For a glide APPROACH it will actually have no effect. OK if you're flying a different type of circuit be it low level or a gliding CIRCUIT then fine call it because it will help people work out where you are.

Once you've decided that the throttle can be closed things really will not look a great deal different apart from being a little above the usual 'glidepath'. Actually of course you are on the glide and all the others are flying below it. Which neatly brings us back to go. I try and fly all my approaches as glides and that gives plenty of time to avoid shock cooling by gently reducing power in the earlier part of the circuit.

[llanfairpg]

More important to call flapless approach than glide approach for following traffic otherwise the flapless pilot extends downwind with the following pilot turning base in the normal position and oops we meet near finals.

'Shock cooling' more folk lore!!!!!!!!!!!!!

[IRRenewal]

Much more important to fly the A/C rather than make any of these 'glide approach' or 'flapless approach' calls, none of which I can find any reference to in CAP413.

[18greens]

Thats another one, why do flapless approaches need to be flatter or go out further than normal approaches? If you have such a surfeit of energy why not just apply less power and maintain the glide path. Given the wide variety of approach methods and variety of ac you do see one mans long final is another glide approach. Talking of steep approaches have you ever followed one of those powered hang gliders.

So the priority is to ensure everyone knows where everyone is and getting a priority of landing established. What value is there in calling glide or flapless?

[Contacttower]

Thats another one, why do flapless approaches need to be flatter or go out further than normal approaches? If you have such a surfeit of energy why not just apply less power and maintain the glide path.


In a light aircraft at least flapless landings don't require a flatter approach path and the approach profile is so similar to a normal landing that I don't think it's worth calling. A 10kt or so increase in threshold speed is the only difference usually.

Also if you say on the radio: 'Flapless approach' (which I have heard before) it doesn't really help other pilots much....if you are going to extend the downwind...the say so, it's much more meaningful than saying 'flapless approach'.

I'd always call a glide approach...I think the approach profile is different enough to warrant it.

[Chuck Ellsworth]

'Shock cooling' more folk lore!!!!!!!!!!!!!

Chit, now I have to go and use black out on all my P&W and Wright radial engine manuals.....

Especially my manual for the C117 because there are many " Warning " notices in that outlining the danger of cylinder choking due to shock cooling.....

....we could get into reverse bearing load caused by high RPM and low manifold pressure but I won't go there now.

If shock cooling is a factor in engine life in big radial engines can someone explain why the laws of physics should be different for other air cooled piston engines?

[llanfairpg]

How about because all the cylinders are exposed directly to the airflow in a radial and not in other layouts as found in most Uk training aircraft, hence the lack of similar placards.

[llanfairpg]

In a well discliplined circuit with max 4 aircraft(which should be an 800 feet oval for my money) everybody would always be in the same position. However the circuit pattern at a lot of airfileds is just a free for all based more on need than organisation and management

[Chuck Ellsworth]

How about because all the cylinders are exposed directly to the airflow in a radial and not in other layouts as found in most Uk training aircraft, hence the lack of similar placards.

Well...lets examine air cooled engines.

Do they need airflow evenly past all cylinders to properly cool each cylinder?

Is it possible that because engines such as the little Continentals and Lycomings do not have their cylinders evenly exposed to the air flow like a radial the engine manufacturers require baffling to evenly spread out the airflow to evenly cool all cylinders?

Anyhow this will get us nowhere.

[davidatter708]

The tighter the circuits the better i think not only does it mean u can glide in but that you can save about £5 by not doing bomber circuits. But never cut othjer people up.
David

[llanfairpg]

Tighter circuits produce better handling pilots, in my experience

[White Bear]

I was told that in the early days of flying many engine failures occurred as the pilot altered the power setting on his engine as he approached the air field, especially after the engine had been at one power setting for a long period. As to why the engine should suddenly fail at this point is not clear to me, but this was the reason given for his instruction. “Always be within gliding distance of the air field before you make any power reduction”.

Could this be the origin of the military method of chopping power when opposite the numbers on the down wind, and make a curved dead stick approach and landing?

Personally I look upon each landing as a unique event, and treat it as such. I do whatever I need to, in order to hit the numbers. :ok:

Regards,
White Bear.

[UV]

Seems that lots of people here think that practicing glide approaches (with the engine throttled back to idle) and then doing the same thing, with a genuine engine failure, will enable them to reach the airfield on that awful day.....have they never witnessed the difference in the gliding performance of an aircraft with an engine throttled back, as opposed to a genuine "deadstick" engine???? Guess not.

Regarding "the Shock cooling, more folklore" well Chuck you are right ....its beyond help!!
UV

[kiwi chick]

UV

.....have they never witnessed the difference in the gliding performance of an aircraft with an engine throttled back, as opposed to a genuine "deadstick" engine???? Guess not.

Yes.

[Mark1234]

True deadstick, no - and I hope not to have to, but I'm expecting significantly worse glide performance, and hope I'll be able to cope.. after all, the 172 at idle glides a lot worse than a duo discus in just about any config ;)

As for shock cooling, plenty of cracked heads on pawnee glider tugs would indicate a genuine problem, as would the SOP's glider clubs come up with to look after the things.

[kiwi chick]

Mark1234

True deadstick, no - and I hope not to have to, but I'm expecting significantly worse glide performance

:hmm:

I suggest you find an experienced instructor and give it a go.

[shadowoneau]

after all, the 172 at idle glides a lot worse than a duo discus in just about any config
A 172 at idle glides a lot worse than a AS-K13 in it's only configuration.. :)

[BroomstickPilot]

When I learned to fly, in 1960, the term shock cooling just wasn't heard. I'm sure I never heard it once. I was taught that the reason you rev the engine occasionally when flying throttled back, perhaps during a PFL or a glide approach, was to prevent the plugs oiling up in our inverted, in-line engines. The only time we consciously managed our engine temperatures was immediately after starting and when we cooled the engine after landing, immediately prior to shut-down.

The engines in use then were the air-cooled, in-line, inverted, four-cyllinder de Havilland Gypsy Major and Blackburn Cirrus Minor II. And the majority of our instructors then were ex-wartime military pilots with extensive experience on a whole variety of engines including big air-cooled engines.

When I returned to flying a couple of years ago, I encountered this concern with shock-cooling for the first time. And the concern was real. I know for a fact that today gliding clubs in particular do have a constant problem with cracked cyllinders, caused after dropping the tow and returning as quickly as possible to the launch point to collect the next tow.

I wonder whether the current concern with 'shock cooling' could have something to do with the fact that for most of the last forty years private flying has been utterly dependent on the Lycoming and Continental engines. I wonder if these engines are more susceptible to variations in temperature than the engines we used to use.

Broomstick.

[First_Principal]

Broomstick, you've probably got a point there - I was looking at a Gypsy Queen today (I think!), actually two of them in a Devon. They clearly have a great deal more mass, and possibly less efficient cooling, than your average small Lycoming or Continental.

These later engines with less mass and more efficient (relatively!) cooling will alter temperature at a faster rate, potentially leading to greater thermal stress and the cracking etc that others have noted. Just the same sort of thing where you can heat up a glass, then dunk it in cold water to make it crack - but if you heat it up slowly to the same temperature, then cool it slowly it won't destroy itself. Somewhere in between these two extremes will be a level of change that is acceptable for the glass, or engine, in terms of both thermal stress and practical use. There are also a number of other factors involved with engines, including changes in clearances due to temperature etc.

I'll admit that, like Chuck, I've been made more aware of this with respect to the P&W engines but from a first-principles perspective it's a no-brainer and almost any engine could be affected in some way.

As Pilots we have the ability to make or break the engine, particularly over time. Amongst other things smooth changes in throttle level and being aware of the induced temperature changes and resultant stresses involved will assist in ensuring a longer-life engine as well as improving the life chances of the Pilot & Pax. It doesn't really cost anything, and in the long run could save money, so why not?

[old,not bold]

Other than good practice, I don't think I really understand the logic. If anything the engine is less likely to fail at a low power setting during final when compared to any other part of the circuit (carb ice discussions to one side for the moment, that is down to equipment and technique).Going back a bit in the thread, I know.

So what's wrong with good practice? And can you casually put carb ice discussions to one side?

What I cannot understand about this thread is why anyone would want to carry out a low, powered approach when they don't have to under normal visual conditions, as opposed to a glide final approach from the start of the base leg or from a straight-in approach. Unless the wings fall off a glide approach is going to succeed, assuming you chop the power and set carb heat at the right moment, and you can always get rid of excess height in a slip. A powered low approach carries a risk of engine failure, however small. Why take the risk if you don't have to?

As for big wide circuits with long approaches for ab initio students, I have always thought they are fraudulent. To only get 4 landings in an hour's flying is a total waste of a student's money, and students are well-advised to avoid schools where this happens, which probably means avoiding schools based on busy airports.

PS The reason I was taught to use a 15-sec burst of power with any engine with a carburetor (spelling?) every 500 ft in a PFL or such-like was to get rid of/prevent carb ice, as well as, with a Gipsy Queen only, to clear the plugs and see if the mass of iron was still functioning at all.

[bjornhall]

So a glide approach succeeds, if you do it right. A forced landing following an engine failure is also succesful, if you do it right. But which are you more likely to screw up; one out of 1,000 approaches with the engine running, or 0.01 approaches with an engine failure?

Which accident type is more common: Having an accident (no, not that kind! :E) after suffering an engine failure during the approach, or flying oneself into an accident by misjudging the landing, either going off the far end or crashing during a mishandled go around?

If one agrees that landing accidents due to misjudged approaches are much more common than accidents following engine failures during approach, and if one further agrees that a powered approach is easier to judge and control than a glide approach, I think one should limit glide approaches to what is necessary for engine-out proficiency and let powered approaches be the normal procedure.

Which, incidentally, is how I'm being instructed to do it...

[gasax]

I would suggest that if you can only land with assistance from the engine then you are severely limiting your options.

Fine when you're learning to fly and the work load is already high but if you skill levels require engine assistance for all landing you chances of getting it right on the occasion you reaally need to is going to be pretty small.

[Chuck Ellsworth]

Quote::::


As Pilots we have the ability to make or break the engine, particularly over time. Amongst other things smooth changes in throttle level and being aware of the induced temperature changes and resultant stresses involved will assist in ensuring a longer-life engine as well as improving the life chances of the Pilot & Pax. It doesn't really cost anything, and in the long run could save money, so why not?

[Mark1234]

Sorry for the thread drift:



Quote:
True deadstick, no - and I hope not to have to, but I'm expecting significantly worse glide performance
:hmm:

I suggest you find an experienced instructor and give it a go.

Kiwichick:

I'd be interested to, however you're rather lucky to find an instructor who will even contemplate deliberately stopping the fan in flight - it leaves little option if the scenario doesn't go according to plan. I'd take bets that 99% of pilots are in the same boat as me!

Maybe I'm in a better place than most in being an active glider pilot, or maybe I'm just cruising for a fall (hope not!), but I can't see the biggie - the whole plan is you have to work to what the aeroplane is achieving in the glide; fly a different plane, and the parameters change, as they do having a truly dead engine. Forget the formal rectangular circuit, and fly the circuit to get you there - roughly a constant angle to aiming point. Should be quite achievable.

I'm more concerned about what happens when: 1) It coughs on final with full flap and a 1500rpm powered approach. 2) What if the fields along the nice straight course you're flying aren't very landing friendly? I'm told to trust the engine, but low hours powered, and still flying with a slightly different mindset!

While on that: how many have actually touched down in a paddock on a (P)FL? Have done a few live landouts myself, though never in a fan assisted aeroplane.

Incidentally, I was lucky enough to spend some time gliding in kiwiland recently (Omarama). Probably one of the prettiest, and scariest places I've flown - hanging in almost silence at 15000ft over mt cook will stay with me for a long time!

Shadowoneau - ah, the old 13. Fond memories :) Crack those brakes open, and it's a LOT worse than a 172. I think the duo on with brakes is almost a better glide than the 172, which is what I was (jokingly?) digging at :)

[bookworm]

If one agrees that landing accidents due to misjudged approaches are much more common than accidents following engine failures during approach, and if one further agrees that a powered approach is easier to judge and control than a glide approach, I think one should limit glide approaches to what is necessary for engine-out proficiency and let powered approaches be the normal procedure.

Excellent point. I've seen very few reports of accidents (particularly UK ones) due to engine failure on final: can anyone supply any examples?

[18greens]

Thanks for all of your replies, some interesting debate.

So from what everyone has said there did not seem to be a sea change from glide to powered approaches at a specific point in time.

[Tony Hirst]

Old Not Bold,
So what's wrong with good practice? And can you casually put carb ice discussions to one side?
Twas my text you were quoting. There are two sides to this, fear of engine failure and so ensuring you can reach the field or just doing glide approaches for good practice. I wasn't dissing good practice, I was trying to home in on what I thought 18G was getting at: that we should do glide approaches just in case like they did on the old days. That is what I was questioning the logic of as I explained in my usual obfuscated manner. If you want to do it for practice then feel free, I don't see any reason why not, it is good fun for a start and I didn't mean to imply otherwise :ok:

With regard to carb ice, I really couldn't be bothered trying cover every possible nitty gritty angle, CH is a relevant to some but not to other pistons in different ways to greater or lesser extents :\

[Contacttower]

True deadstick, no - and I hope not to have to, but I'm expecting significantly worse glide performance



I've always wondered about this, does an idling prob actually produce more drag than a stationary one...especially if its three bladed?

[BackPacker]

I've always wondered about this, does an idling prob actually produce more drag than a stationary one...especially if its three bladed?

Contacttower, unless there is a massive internal failure (a broken crankshaft for instance), don't expect the prop to be stationary. It will be windmilling, and a windmilling prop will cause more drag than a prop that's running at idle. After all, at idle there's at least a minimum amount of fuel going into the cylinders helping the prop tick over.

What I've heard is that a stationary prop will cause less drag than a windmilling one, but in order to get the prop really stopped you've got to slow down to something very close to stall speed, usually. That's not something you're going to do with an engine failure, unless you've got steel nerves and plenty altitude to spare.

I'm flying aerobatics, including negative g manoeuvres, in an aircraft without an inverted flight system. So far I haven't been in the situation where the prop actually stopped, but one of these days I'm going to take the aircraft up high and deliberately find out at what speed the prop stops windmilling, and what speed is required to get it going again.

[RatherBeFlying]

There is a major difference between failure to find lift and engine failure, ie. a sink rate of a 100'/min or so compared to 800'/min.

In a glider at 2000' AGL, you have some 8-10 minutes to pick out a field within 4-5 miles and 200 yards is plenty long. A well managed landout is a leisurely process.

If the donk quits at 3000' AGL you will be at your 1000' key point in 2.5 minutes which has to be within about 2 miles plus you need more like 400 yards.

When I have to fly low, I find myself picking out fields and staying within reach.

As for difficulty of judging approaches, I've always found steeper approaches easier.

Getting the sight picture of a tight approach well burned into the brain is good preparation for that day when you might need it.

[UV]

To those who think glide approaches should be the norm..have you really considered the matter in the 21 st century? Bit like accepting GPS?!

For example have you considered the difficulty fitting it in with other traffic? Have you ever been trying to teach it and been frustrated at the time spent trying to find a suitable gap in traffic? That is the reason for telling Air Traffic you require one!

For those of you who do it every time....do you really subject your novice passenger/grandmother to a sudden and total reduction in engine power on base leg and then what, to them, appears to be a suicidal dive to the Airfield? Do you?

For those who operate from private strips (frequently small and often demanding)...do you really do it when a short field "performance" type approach is really what is required?

For those who fly heavy complex singles..do you ever do it in one of these types? Do you?

For those who fly twins...ever do one in a twin?!

For those operating from Regional airports...how do you manage them all the time? Same applies to those operating from busy GA fields.

And what does this bog standard glide approach "training" achieve when the performance may be nothing like a genuine engine failure which can vary from a catasphophic failure to a bit of carb ice, all of which may require differing actions!

So, who is doing them as a matter of course and what are they really achieving?

UV

[robin]

>>>>>>>>>>For those who operate from private strips (frequently small and often demanding)...do you really do it when a short field "performance" type approach is really what is required?<<<<<<<<<<<,,

Sorry, must be my old age. Can you define what a "short field performance approach" is

[kiwi chick]

don't expect the prop to be stationary. It will be windmilling

oh, contrare...

What I've heard is that a stationary prop will cause less drag than a windmilling one, but in order to get the prop really stopped you've got to slow down to something very close to stall speed, usually. That's not something you're going to do with an engine failure, unless you've got steel nerves and plenty altitude to spare.

Firstly, I don't have nerves of steel. Let me make that clear. There was a definite requirement for Changing of the Undies.

My prop stopped completely - probably due to the fact that we had just gone through to full power at the beginning of a go-round, so were indicating 60-65 knots. :eek:

From what I noticed, [in between my cursing, hoping there really IS no hell, and thumping my student] we glided better.

Or maybe it was just that time slowed down. Who knows.

[kiwi chick]

Oh, I almost forgot:

For those of you who do it every time....do you really subject your novice passenger/grandmother to a sudden and total reduction in engine power on base leg and then what, to them, appears to be a suicidal dive to the Airfield? Do you?

I beg to question what kind of Pilot you are if you imagine this would ever happen.

I always - and I mean ALWAYS - tell my pax what is going on with the aircraft at any phase of flight - especially when I'm about to reduce power. If they know what to expect, and see me looking completely relaxed, then I'm not "subjecting" them to anything.

And what does this bog standard glide approach "training" achieve when the performance may be nothing like a genuine engine failure which can vary from a catasphophic failure to a bit of carb ice, all of which may require differing actions!

So, what you're saying then is because it MAY not be like the real thing, we shouldn't practice them?

Best we stop teaching/practising stalling, spin recovery, precautionary landings, forced landing without power as well. :ugh: :ugh:

[BackPacker]

My prop stopped completely - probably due to the fact that we had just gone through to full power at the beginning of a go-round, so were indicating 60-65 knots.

kiwichick, care to expand a little? What type of plane, what type of engine? In our R2160 I regularly fly inverted (without an inverted flight system, so no fuel getting into the cylinders) at approximate those speeds, or a little faster, and my prop keeps windmilling.

Also, what was eventually determined to be the cause of your engine stoppage? Unless it was a catastrophic failure physically blocking the rotation, I would expect that at typical approach/go around speeds, an engine would remain windmilling even if there's no fuel at all going into the cylinders.

[gasax]

UIV I'm a bit baffled - why would a glide approach cause any of the difficulties you quote?

You might be a little higher at the start but given the variability of apporaches I doubt anyone would notice.

You fly pretty much the same speed so how is 'fitting in' a problem?

As for plummeting? Are you a newspaper reporter? Do you treat your engine that way? Cos I certainly never do.

What do I achieve by doing them? I improve my aircraft handling skills, I give myself many more options if the engine every does fail, I maintain a level of currency in terms of judgement which flying an engine assisted PAPI apporach does not exist - actually I have fun too!

[llanfairpg]

Glide or powered isnt an argument that can ever be won, too many opinions mostly based on folk lore. The aim of a PPL is to be able to fly to other destinations and at many airfields it just may not be appropriate to fly a glide approach.

As already stated, glide approaches stems from Tiger Moth days when a/c did not have flaps and engines were not so reliable.

What is more important is the ridiculous wide circuit patterns flown by some schools.

[LowNSlow]

I fly behind a 66 year old engine (it has been rebuilt a few times) and I prefer to slow down at the end of the downwind and then make a curving approach at idle power with full flap (effective) and using sideslips as necessary to position for the end of the runway. Carb heat isn't an issue as it is automatically on when the throttle is set for anything less than full power. I always feel that I've let myself down if I have to touch the throttle.

I feel that glide approaches should be practised as you are effectively practising a PFL without any possibiliity of breaching the 500' rule.

One instructor I flew with had a great way of focusing the attention of his student. He'd get the student to position the aircraft over the middle of the airfield (3 runways ex B-24 base) and then turn the magnetos off. :eek: Certainly got the attention of the occupier of the LHS.

[Mark1234]

Ratherbeflying: I think you rather overstate the difference - 1kt min sink from a k13 is on the ambitious side, and I'm pretty sure the 172 doesn't do 8kt down at best glide - not with both wings attached in any case. I'd also argue that 2k is rather high to have picked your field, but that's beside the point.

Realistically there are a multitude of approaches between the idle, full flap glide (steep) and the drag it in over the hedges with the engine working hard against full flap. Surely there's a certain degree of discretion as to what is appropriate for the aeroplane and the circumstances. Being a paranoid type, I tend to err towards the high side on the basis it provides the greater margin of safety. Sure engines rarely fail on short final - but that's little consolation IF it happens to you. I also try to be gentle on the engine. But I'm merely a low hours PPL treading carefully.

[RatherBeFlying]

Mark1234, Agreed the 2-seater trainers come down faster and are generally best kept within range of the home field. Fibreglass single seaters have minimum sink in 100-120'/min range.

800'/min is something I'm quite used to seeing in a C-172 at idle, generally with 20 flaps; about the same in a Citabria.

At 2000' in a glider, I'm starting to look for fields, especially as at that level you're generally below the working band. While all the time I'm looking for lift, I do want to have a good field in my pocket by the time I'm down to 1,500. Once I have that the name of the game is to find sufficient lift to get away before I'm down to 800' at which time I've run out of quarters and it's time for the downwind.

[llanfairpg]

None of the above is an argument for using the glide approach in favour of a powered approach.

The best approach is the one that brings you over the hedge at safe altitude and airspeed and provides a safe touchdown point.

I went into LHR once in a C172 and they asked me to keep 120 kts for as long as possible to the threshold, I couldnt really say sorry i only do glide approaches!

The only argument I can see for glide approaches are training and practice.

[Mark1234]

Just for the record Ratherbeflying I retract my previous - did a checkride in a warrior today and attendant PFL - thermic day, was seeing anything between 500 and 900 down - say an average of 700 down, definately in the ballpark and obviously flaps will worsen the angle (good reason to keep them hidden until really sure!). FWIW I'm also in line with your expanded version of outlanding procedure - most of my XC has been done in the UK where the working band is generally fairly low.

[kiwi chick]

Backpacker... (sorry for delay don't have internet at home)

Cessna 152, Lycoming 4 cylinder, no catastrophic failure, no fuel blockage.

And, again, the prop definitely stopped and there indeed was NO fuel going to the cylinders - my student had turned it off.

(as anyone who has flown a C152 will know... you cannot see the fuel cock, you can only feel it... and as I cannot fathom any sane reason why my student would turn it off, I did not check it every two minutes.....)

[LowNSlow]

kiwi chick had the engine recently been overhauled thus giving the cylinders a higher compression ration than a half life engine? Conversly, backpacker, how many hours does the engine in the R2160 have on it?
The one time I had my engine cut on closing the throttle the prop did stop but I was only doing 40mph at 5' above the runway so I didn't have a chance to evaluate any improvement in gliding characteristics :hmm: but I did notice the sudden loss of residual thrust. It wasn't the best landing of my life :}

[vee-tail-1]

Just my pennyworth.. During my PPL training on Cherokees in South Africa, shock cooling was not really a problem with air temps regularly above 25 degrees. So we did glide approaches on every landing.
I queried whether the prop would stop with an engine failure, so we stopped the engine overhead the airfield to see what would happen. Result it kept going until approx 60 knts, thereafter we followed the checklist and cracked open the door. Can't remember the actual rather high rate of descent, but the sight of that prop blade sticking up in front of me was quite intimidating. :uhoh:

[BackPacker]

Conversly, backpacker, how many hours does the engine in the R2160 have on it?

It recently got a new engine, or top overhaul or something. Don't know exactly, only we were not allowed to do aeros with it for the first 25 hours. My guestimate is that by now it's got somewhere between 100 and 300 hours or so.

Haven't had the nerves yet to pull ICO at FL55 in the aerobatics area yet to see what happens, record glide performance etc. Problem compounded by the fact that at my home airfield (Rotterdam), the CTR only extends to 3000', with the class A Schiphol TMA on top, and these sorts of stunts are generally not appreciated there. And with the end of the year looming at work, and things to do in the weekends, I've got the feeling that my flight last weekend was the last for this year.

[kiwi chick]

Haha, it is quite unnerving isn't it? Looking at it, thinking "I'm not supposed to SEE you..."

I went and did a deadstick with our CFI afterwards from overhead the field, and I don't recall that we had any problems getting it to stop? Maybe we pulled back to nearly a stall, I can't recall.

Amazing how much calmer I was with someone more experienced beside me - mind over matter?! I mean, there was no way we were going to miss the runway - even I'm not that bad! :}

[llanfairpg]

It will stop depedant on airspeed

[moggiee]

'Shock cooling' more folk lore!!!!!!!!!!!!!
Tell that to the folks who use Lycoming powered glider tugs and they'll brain you!

Keeping power on to allow the rear cylinders to cool slowly makes a huge difference to the mean time between failures. Now, it may not be relevant of a relatively cool circuit, but it certainly does apply to engines which have warmed up nicely in a high power climb - just 20-30 seconds of so of level flight before pulling back the throttle and subjecting the cylinders to increased airflow in the descent can make all the difference to engine life.

[SkyHawk-N]

I do a lot of glide approaches where I fly from. Depending on how busy they are, it's regularly advisable to keep a very tight circuit and remain in sight of the control point, 40 degree flaps help a lot.

[llanfairpg]

Shock cooling' more folk lore!!!!!!!!!!!!!

Towing gliders is a little bit different from a glide approach in the circuit

After a long full throttle climb with the added weight of a glider followed by an instant high speed descent it would be rather foolish to close the throttle in any aircraft but you do not need a placard to remind you of that or do you?

[IFMU]

Both clubs I've towed for we run downhill at 2400 RPM and high speed, 120-140 mph in the pawnee. I fly my final with the throttle at idle, and judging by the steepness of the approach of my fellow tow pilots most of them do too. Our engines typically go to TBO, no cracking. One thing that helps them get to TBO is they are flown a boatload.

-- IFMU

[BackPacker]

Sorry for resurrecting this thread. But it was a beautiful day today and I finally managed to get over my nerves..


Haha, it is quite unnerving isn't it? Looking at it, thinking "I'm not supposed to SEE you..."

I went and did a deadstick with our CFI afterwards from overhead the field, and I don't recall that we had any problems getting it to stop? Maybe we pulled back to nearly a stall, I can't recall.

At FL55, class E and a block altitude of 3000" to FL55 assigned by ATC, with an emergency field in sight, with 2000 RPM, carb heat on, fuel pump on, and maintaining 80 knots, I finally decided to pull ICO to see what would really happen. As expected, the prop windmilled. Restoring the mixture got it going almost immediately. Good.

Next test. ICO and then try to stop the prop by reducing airspeed. Deep into the stall, almost spinning, but still a windmilling prop. Restore mixture, climb back to FL55. Good. I now know that the engine will keep windmilling whatever the airspeed, unless there is a massive internal failure or unless I do something really stupid.

Try again. ICO, reduce airspeed to about 60 knots, then pull up into a half-g pushover to get the speed well below Vs without getting into a spin. Finally, the engine stops completely. Stationary prop in-flight. Funny thing is, it did not scare me one bit because there still was a lot of wind noise. Restore speed to about 80 knots, key to start position. Engine roars into life after three or four blades. Perfect.

Back to altitude, now for the real test. ICO, Pull up, half-g pushover to get the prop stopped again. Restore the mixture and now dive to see if the airspeed can get it working again. I lost a good 1500" to get to 140 knots but once I got to 140 knots: one blade, two blades and then the engine roars into life again.

So what did I learn today about the R2160? First, the engine on this particular bird will windmill until the airspeed drops below about 40 knots, well below Vs. Restoring the mixture will almost immediately bring it back to life. Second, a stationary prop only needs a small nudge of the starter button to get it windmilling again. And third, a stopped prop on this bird will need about 140 knots to get going again. That requires a 45 degree or so dive and an altitude loss of about 1500".

Of course in another aircraft the numbers will be different but this greatly boosted my confidence in this aircraft. Particularly because it doesn't have an inverted flight system but we do push negative g's in it regularly.

[cats_five]

Mark1234, Agreed the 2-seater trainers come down faster and are generally best kept within range of the home field. Fibreglass single seaters have minimum sink in 100-120'/min range.
<snip>


Of course it all gets a bit worrying when everywhere seems to have 4-6 knots of sink...

[shortstripper]

Where's the mystery? :rolleyes:

A stopped prop will cause less drag than a windmilling one. An idleing engine turning the prop will cause less drag than a windmilling or stopped prop. Which ever you are faced with, you simply judge the glide angle it is giving you and fly the approach accordingly. Aircraft engines will windmill unless the speed is bled off sufficient for the tuning force of the air hitting the prop to be overcome by forces acting within the engine to resist motion. Newer engines that are still tight, or ones with higher compression ect will stop at higher airspeed than older or low compression ones. Also prop pitch/diameter will also have an effect. Certainly, if I turn off the ignition off, on my VW it will stop dead! Mind you, my max airspeed is only 70knots :)

I don't fly glide approaches every time, if I did in my T31 I'd be moaned at every time I went to an airfield other than my home strip. However, I prefer to be within gliding distance of the field if possible and get very peeved at the bomber circuits adopted by some (noise abatement permitting).

SS

[mark sicknote]

Here is my humble take on the question:

I would far rather be caught engine off when flying a tighter circuit that was conducive to glide approaches. Someone earlier quoted that 30% of
GA accidents occured on approach and the option to glide it in would be preferable to becoming stuck behind the energy curve.

The flip-side is that flying tighter circuits encourages steeper turns onto final / base leg placing more pressure on inexperienced pilots to overbank in the turn, thus making them succeptable to stall / spin incidents.

The question is, are more accidents caused but these type of errors or by engine incidents on long finals when behind the energy curve?

Any takers?

Best,

Sicknote:ok:

[shortstripper]

That's an interesting point Sicknote, and has some merit. However ...

I'd wager that many who are caught in the spin off final turn though, are those used to bigger circuits and then one day (probably under pressure) find themselves having to turn tighter than they're used too and over rudder! A well banked but balanced turn, if flown properly, is far, far safer than being frightened to bank and subconciously trying "will" yourself around the turn and applying that bit too much rudder. Take a slipping turn as an example, you can have bootfuls of out of turn rudder applied, a crazy bank angle and huge amounts of sink ... but you will not stall and spin. If inexperienced pilots were taught to be less frightened of banking, but not allowed to fly out of balance when doing so, there would probably be a reduction in such accidents.

SS

[Sedbergh]

The BGA instructor's "how to damage yourself spinning" scenario goes:-

a) You're a bit low in the circuit
b) Instead of modifying the circuit you continue to fly your "normal" pattern but subconsciously keep the nose a bit high (= speed decay without a noisy lump on the front of the aircraft)
c) You're now low on the final turn and start worrying about wingtip meeting trees or whatever, so you keep the bank shallow
d) But now you're not getting round the final turn quickly enough so you feed in more rudder

Then insert your final words "Oh f..." as the world rotates:(

PS The above is only demonstrated at a very safe height. But especially in a Puchacz it certainly gets the pupil's attention!:ooh:

Ergo: - It ain't steep turns on finals that get you, it's the slow shallow ones!

[cats_five]

The BGA instructor's "how to damage yourself spinning" scenario goes:-

a) You're a bit low in the circuit
b) Instead of modifying the circuit you continue to fly your "normal" pattern but subconsciously keep the nose a bit high (= speed decay without a noisy lump on the front of the aircraft)

And you are also flying below best L/D speed so things are getting worse than they would be at the correct speed...


c) You're now low on the final turn and start worrying about wingtip meeting trees or whatever, so you keep the bank shallow
d) But now you're not getting round the final turn quickly enough so you feed in more rudder

Then insert your final words "Oh f..." as the world rotates:(

PS The above is only demonstrated at a very safe height. But especially in a Puchacz it certainly gets the pupil's attention!:ooh:

Ergo: - It ain't steep turns on finals that get you, it's the slow shallow ones!

Agreed about steep/shallow turns.

There is also the demo of what happens if you turn without enough airspeed after a winch launch failure that usually gets attention, even in a K21... Especially when the instructor sets it up and says 'you have'.

[Mark1234]

I seem to recall it goes something like: Pitch into a steep climb with speed; as the airspeed decays to launch speed, pretend the wire broke, commence a pitch towards horizontal, but not to vigorous.. arrive flat at something significantly underneath regular stall speed, still flying 'cos you're at significantly <1g. Move the stick back to the regular 'level flight' position, commence a turn (no deliberate mis-coordination required)...

.. at which point the world flips and starts rotating :D

Puch was the first aircraft I spun that the rudder floated onto the stop and stayed there - i.e. required positive recovery rather than releasing the pro-spin controls.

Interestingly I'm currently doing powered aeros in a R2160! Not spun it yet tho..

[RatherBeFlying]

As before stated, it's the shallow turns that subconsciously get "helped" with a bit of rudder that are more likely to get you into an unexpected spin.

I've spent a few hours thermalling the Puch solo close to the stall and have no complaints with its behavior in a steep bank.

But it sure spins easy out of a shallow bank with not much back stick force and a lot of people have gotten killed that way in the Puch.

Spring checks are coming up and I plan to ask for an extra thousand feet or so to see how/if the Puch spins from a 45 degree bank.

Derek Piggott in his books somewhere mentions that a glider won't stall in a 45 degree turn because the elevator does not have the power in the angled airflow to stall the wing. Caveat that in gliders, pilot position, weight, ballast, equipment and other CG factors can yield an a/c that can vary from impossible to stall to one that's precariously close to the stall.

[BackPacker]

Interestingly I'm currently doing powered aeros in a R2160! Not spun it yet tho..

A likeminded soul at last!

Spinning the R2160 is entirely conventional. In fact, now that I'm doing aeros in it and finally learning what those footrests are for, I find it very hard to make a nice, clean spin entry. It's as if the elevator runs out of travel before reaching a low enough speed for a nice entry. Particularly when the aircraft is comparatively light: one-up and half fuel. Even when you whack on the rudder it is really hesitating to start the spin.

Once in the spin though it's all conventional: release the pro-spin controls a little after three quarters of a turn and you are out of the spin at exactly one turn. Push to the vertical, hold one second, pull straight and you've got about 110 knots - perfect for the next figure in the sequence.

[cats_five]

I seem to recall it goes something like: Pitch into a steep climb with speed; as the airspeed decays to launch speed, pretend the wire broke, commence a pitch towards horizontal, but not to vigorous.. arrive flat at something significantly underneath regular stall speed, still flying 'cos you're at significantly <1g. Move the stick back to the regular 'level flight' position, commence a turn (no deliberate mis-coordination required)...

.. at which point the world flips and starts rotating :D

That's the one. If you are lucky the instructor does it at altitude, if you are unlucky they do it following a simulated high winch launch failure (but maybe only in a K21, not a Puch), if you are really unlucky the put you in that situation (again maybe K21 only!) and hand control back. At least one knows the K21 will convert fairly swiftly into a spiral dive...


Puch was the first aircraft I spun that the rudder floated onto the stop and stayed there - i.e. required positive recovery rather than releasing the pro-spin controls.<snip>

The DG500/505 is 'fun' as with that huge canopy the earth is clearly going round at one's feet. :eek: :ooh: :yuk:

[rans6andrew]

no body has mentioned the recent failure of a powered approach at LHR. I know that the big jets need to keep a load of power on because their jet engines don't spool up very quickly from ground idle but it does illustrate the problems that it can lead to.

Still working up to stopping the 503 on my Rans and bringing it in. No chance of a restart while airborne as the pull starter is between the pedals and behind the stick, I can't do it from inside the cockpit even while stationary on the ground. I will find out how much a stopped prop changes the glide slope.

Andrew.

[shortstripper]

Hmmmm! I'm all for being within gliding range, but I'm not sure I'd apply that to airliners :rolleyes:

Different kettle of fish altogether, but it would be interesting to see the captains taking wagers from the first officers as to who could chop power the furthest away and still make the threshold :E Look out for slipping 747's or Airbus downwind run's with Chandelle style pull ups to land into wind whilst dumping fuel! Weeeeeeeeeeeeeoooooooooowwwwwwwwww!!!! :}

SS

[Sedbergh]

I heard a story from a BOAC 2nd officer a few (well a lot!) of years ago about him & his Captain discussing the feasibility of landing a VC10 without power. 2nd had then tried it at Khartoum but had had to add lots of thrust to get in. Capt had then gone into Nairobi starting at about 10 grand over the Ngong hills (Nairobi airport is at about 5 grand) and had sucessfully plonked it onto the end of the runway. Don't know if it was true though!:uhoh:

Of course there have been a couple of successful glide approaches from height with airbuses since!:ok:


Both a/c sustained some damage I believe, but excellent airmanship. All a question of having speed & height relative to runway.

But if you're low & slow & your 777 engines see fit not to spool up!:=

p.s. I believe pre-WWII the standard RAF practice was a glide approach, with drinks having to be bought in the mess for anyone having to open up on approach. With the advent of heavier monoplanes the undershoot accident rate got too high & powered approaches were mandated. Can anyone confirm?