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Glide approach to land technique

Old 30th Mar 2019, 13:19
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Glide approach to land technique

I am reading "The Skies the Limit - My flying Life" by former Wing Commander Eric Read AFC. I flew with Eric on several occasions when we were both at the DCA Flying Unit at Essendon in the 1960-70's. Part of the foreward of his book had this:
ROYAL AUSTRALIAN AIR FORCE
HONOURS AND AWARDS
AIR FORCE CROSS

WING COMMANDER ERIC VERNON READ
CITATION: Promulgated in the Commonwealth of Australia Gazette on 27 June 1946

As commanding Officer of No 200 Flight, Wing Commander Read has displayed exceptional skill, courage and devotion to duty. He has completed 254 hours flying on the secret and dangerous special missions carried out by the Unit, and his outstanding leadership has contributed considerably to the high standard of efficiency which it has attained.

The success of these missions has proved of the greatest value to the operations in the South-West Pacific area, and has contributed to their successful conclusion.

Group Captain V.E. Hanncock.
............................................................ ............................................................ ............................................................ ................................

Eric Read joined the RAAF in 1935 and went solo in Tiger Moth A7-3 on 4 June 1935. He describes that flight thus:
"It was after I had resumed my flying training, when what can be called the ultimate aim of every budding young pilot came about, that is to be sent solo.This great event took place on the 4th of June 1935 when, after 45 minutes with Max ‘preening’ me, Squadron Leader Banting in A7-23, accompanied me whilst I demonstrated for 20 minutes how an aircraft should be flown! I did quite a good landing and with a few words of encouragement, he got out of the front cockpit, taking the joystick with him and I think muttering to himself, "Go and break your own bloody neck, your not breaking mine”

I taxied back, turned across wind, all clear, lined up and opened the throttle, eased it off and I was airborne. What a thrill, here I was all by myself, and I must admit the front seat looked awfully lonely without that head barking insults and instructions to me. I recall that when I was safely airborne I gave vent to my jubilation by yelling my head off, nothing in particular, but from the sheer joy of being up here alone on this memorable occasion. I was flying free, up with the birds (not away with them) sharing the domain that has been theirs for eons, with the sight of mother earth below me.

I carried out several medium and steep turns, throttled back and carried out gliding turns, “ah Read, your flying can be likened to the touch of a master and the caress of a mistress”! who's kidding who? Enough of this love talk, get this contraption back on the ground in the same condition as when you took it off, now concentrate ‘knuckle head’, and remember all that you have been taught.

Pick up the wind direction from the wind sock, and join the circuit on the down wind leg at about 1000 feet. Close the throttle and trim the aircraft for a gliding approach. Turn across wind and commence a series of ‘S’ turns, each turn bringing you lower down and closer in. Turn into wind, tending to overshoot, slip off any surplus height and land straight ahead."

In reading his description of his first solo I noted it was in a Tiger Moth using a glide approach which was the normal technique for landing in that type in those days. It was also the same technique taught by the RAAF and civilian aero clubs when I first learned to fly on Tiger Moths in 1951 and later as a QFI on the type. It was only on heavier aircraft like the Wirraway that powered approaches became the norm.
When Cessna 150/172 light singles came into the country, their manufacturer's POH stated "Normal landing approaches can be made with power-on or power-off with any flap setting."

Nowadays flying schools universally teach powered approaches as the preferred technique in this type or indeed other similar light singles. Glide approaches are relegated to practice forced landings only. Yet it is a fact glide approaches require more judgement that powered approaches and by the time a student is ready to fly solo in the training area for practice forced landings away from base, he would have already conducted many glide approaches before even first solo.

Why is it therefore that today glide approaches are not taught as the norm when they require superior skill and approach judgement than powered approaches? Disregarding the "S" turn technique used in Eric Read's training days of course it depends on the type of aircraft but in this discussion I am referring to the Cessna and Piper light training types or similar performance singles.
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Old 30th Mar 2019, 13:54
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Centaurus,
Because "being more professional" is the mantra, and the "professionals" are all flying heavy metal and a 3 degree approach slope.

Compounded by the need to fly a "mandatory stable approach" (absolutely necessary in said heavy mental) and a glide approach is "not a stable approach" (from a CASA FOI who can't fly to save himself). A request for the reference to a "rule" that mandated stable approaches in light aircraft did not elicit any answer, not even a wrong answer. Apparently it is NTS ( Non Technical Skills --- previously known as airmanship) but when asked: "Show me where", "no answer" was the stern reply.

Personally, I have no trouble flying glide approaches as the preferred, in any light aircraft, indeed, even in a particular light twin I often fly an approach with barely above idle power --- that one gives abou a 5 degree approach.slope.

Again, apparently sideslipping is frowned upon, "because the heavies don't do it" ---- which, as it turns out, is wrong, most Boeing aircraft on an auto coupled approach sideslip across the wind to track the centerline at low level, except the 747, that uses a combination of sideslip and crab, due engine clearance, and there is no AFM limitation on sideslipping in any Boeing after the B707. -----and "it is dangerous" ??? ----- that from a CFI/Flight Examiner in a GA school.
.
Tootle pip!!

PS: "Being more professional" apparently also requires never shutting up on the radio, never listening before hitting the transmit button, reading absolutely everything back including your collar size, and talking like a machine gun --- also known as the "pingya" system, if you make every call and read everything back, "they can't pingya".
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Old 30th Mar 2019, 14:08
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"Glide approach"

I was taught to maintain a "glide approach" for sloping airstrips,,, especially at altitude, It worked for us!
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Old 30th Mar 2019, 15:47
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It was possible after a little practise to do excellent glide approaches in the 707 and 747 sims, and side slipping worked well if a little too high. Not so sure what the side slipping limits may have been in the real aircraft though!
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Old 30th Mar 2019, 15:57
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Heavy metal glide approaches

Not a problem in my last legacy carrier but in 1979 they decided a stabilised approach was necessary from 300ft..on all types.the regulation was final approach configuration selected by 400ft.
I used a gate of selected by 500ft on short haul and 700ft on the DC10. The latter because some months I only did a couple of landings.
After one of the all engine flame outs we practised glide approaches on the Sims too.
best technique was the French system of constant angle which I taught on sailplanes.
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Old 30th Mar 2019, 21:33
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In the early years of aviation, many aircraft used rotary engines (not radials, mind) so there was no throttle control. The throttle was in effect always wide open and power was regulated by "blipping" the ignition on and off. Coupled with inherent engine unreliability, glide approaches were a safer type of approach to make.

And no, I wasn't taught to fly on rotary engines.... I'm not quite that old!
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Old 30th Mar 2019, 22:12
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I think teaching the glide approach is good idea, but I think we're losing sight of why it was taught to start with.

There is one main reason, Engine reliability. Engines are much much more reliable today to the extent glide approach skills are rarely ever needed.

Remember also in bad old days it was poor form to fly a circuit that put you outside of the gliding range for the runway.
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Old 30th Mar 2019, 22:20
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A mixture of aircraft doing normal powered approaches and others doing glide approaches is tricky at a controlled GA field. Back in my day at least some instructors would notify or even "request" a glide approach. A C152 on a windy day barely passed abeam the threshold before turning base from 1000 ft. But we managed most requests.
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Old 31st Mar 2019, 01:32
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Not so sure what the side slipping limits may have been in the real aircraft though
Test pilot of the 707 Tex Johnson quotes a yaw limit of 15 and cites the exceedance as being the cause of the loss of a Braniff 707-220
The resulting crosswind on the vertical tail forced the rudder to full deflection, overpowering the authority of the rudder control tab. The resulting extremely high roll rate created severe centrifugal loads, which caused engine attaching structures to fail, and three engines separated from the airplane.
Could have been describing the subsequent loss of the RAAF 707.
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Old 31st Mar 2019, 05:49
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Removing all the hairy fairy stuff that is our SOP's what is a glide App? What is gliding? Basically it is a decent/landing without the assistance of some form of fwd propulsion. At the end of the day EVERY A/C App & Ldg is achieved by simply energy management, with or without thrust!
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Old 31st Mar 2019, 09:14
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Very good read.. While in the tower at Butterworth 40 odd years ago on a Sunday a Thai International was on a straight-in approach to Rwy 18 when a flight of four RMAF Tebuans [CL-41G] called for an immediate departure to the East to bomb a few CT's. They were on alert and this happened often. The Thai DC-8-33 was told to maintain 1500 and the Tebs cleared off Rwy 36 not above 500'. They cleared the runway with an early right turn as the DC-8 was approaching a three mile final. I cleared him to land and witnessed a magnificent slide-slip of that big beast and a perfect touchdown. The Captain was a Swede on secondment to Thai. Asked if he could do this everytime!!!
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Old 31st Mar 2019, 09:42
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I did much of my early flying in gliders and it has always seemed natural to me to continue the practice of gliding approaches in light GA.

i fly very tight circuits in the Auster for the very reason my late downwind and base are at 55KN and final at 50 knots or less (sometimes much less). Vs = 26 VFE = 58. If there is someone behind me in the circuit I warn them.

Our little airport at YSHT is being built in with residential subdivision and development. I feel a,lot more comfortable knowing Im within reach of it in the circuit and I worry about long, flat approaches being practised by so many others with engines dragging them in.

Kaz

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Old 31st Mar 2019, 13:48
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A mixture of aircraft doing normal powered approaches and others doing glide approaches is tricky at a controlled GA field. Back in my day at least some instructors would notify or even "request" a glide approach. A C152 on a windy day barely passed abeam the threshold before turning base from 1000 ft. But we managed most requests.
Please forgive a little indulgence in the history and principle of early ab-initio practice forced landings and how and where they were conducted before and after World War 2 at all aero clubs, the RAF and RAAF.

Glide ( known as power-off landings) approaches from the circuit and practice forced landings involving gliding after engine failure, were two entirely different exercises in flying training. The first was considered a normal approach and landing technique from a circuit. The second was done in the training area from various altitudes where an engine failure was assumed to have occurred and the pilot was forced to adopt a glide to reach a field and land.

The discussion subject here is glide approach and landings at an aerodrome. You can easily conduct a glide approach at a busy airfield. For example, if an aircraft ahead of you has extended downwind and you are forced to follow him for separation, you simply maintain circuit height behind him. When on final approach and still maintaining circuit height and you intercept your descent point, then simply close the throttle and glide in.

The glide approach angle in light singles is around 5-6 degrees or more in strong winds. Similarly if you detect an undershoot on final while conducting a glide approach then all is not lost. All you do is apply power and stop descending and fly level until you have intercepted what you judge to be the right time to close the throttle again, then simply do just that and hey presto there you have your glide approach.

That was taught many decades ago and has not changed in principle.
If you finish up high while attempting a glide approach and you already have landing flap down, then go around.

As mentioned earlier, a glide approach from a circuit was never meant to be a practice forced landing. Yet most instructors still erroneously teach it as just that and get the student to cut the throttle either abeam the downwind end of the runway or on the turn to base leg. In turn, that can cause a separation problem and is why several years ago it was SOP to let ATC know what you were up to for separation reasons. All that was quite unnecessary and based on the premise it was indeed a practice forced landing during the conduct of a circuit.

The practice forced landing is an entirely different exercise and was always designed to be carried out from various heights in the training area - and not as part of circuit training.

Last edited by Centaurus; 31st Mar 2019 at 14:19.
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Old 1st Apr 2019, 09:23
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The practice forced landing is an entirely different exercise and was always designed to be carried out from various heights in the training area - and not as part of circuit training.
I realise it was different in ~1940 but in 2019 it is very difficult to legally practice a forced landing to the ground at/near metropolitan airports - impossible off airport and impossible from altitude on airport. Thus, despite your dogmatic pronouncements Centaurus, a glide approach is sometimes profitably used to practice the last part of the forced LANDING given the constraints that exist.

You also do a disservice when you say:

get the student to cut the throttle either abeam the downwind end of the runway or on the turn to base leg
The student should close the throttle at the point at which they judge the aeroplane, based on it's height, angle and distance from the runway, in the prevailing conditions can glide to a safe touch-down point and when to shorten the glide once assured to maximise the LDA. These are skills better learned when the exercise is permitted to continue to touchdown.

One reason glides aren't used routinely is you simply can't fit as many aeroplanes in the circuit if everyone is flying Auster/Tiger Moth style. Powered approaches also allow a greater margin for error, as you said yourself:

If you finish up high while attempting a glide approach and you already have landing flap down, then go around.
Well if you finish up high on a powered approach, you can reduce power and still effect a landing at the proper speed. Or you could even try sideslipping...

I can just imagine the chaos that would result at busy airports if you have every aeroplane gliding from close base until too low then adding power to fly level for a while then back to gliding until too high and going around? What would the 'let's do everything the same way as the FAA because some interpretations of their accident statistics show a lower accident rate or whatever without any regard to the scale, infrastructure and money in the industry there' zealots make of the FAA Flying Handbook description of how to fly a 'normal' approach, and the benefits of a 'power off accuracy approach'?

What was the training accident rate in 1935?

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Old 1st Apr 2019, 11:10
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A "real" glide approach uses the last bits of flap setting to get you over the boundary fence .

(then you get better at it - clearing the boundary fence that is)
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Old 1st Apr 2019, 12:58
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The student should close the throttle at the point at which they judge the aeroplane, based on it's height, angle and distance from the runway, in the prevailing conditions can glide to a safe touch-down point and when to shorten the glide once assured to maximise the LDA.
Read the context where I wrote most instructors still erroneously teach it as just that and get the student to cut the throttle either abeam the downwind end of the runway or on the turn to base leg.
I did not recommend that technique
Anecdotal experience indicates that there are instructors out there that close the throttle on the student in the circuit just before turning base and announce "engine failure - now get in from here" It is the instructor that does the throttle chop - not the student.who chooses the moment to close his own throttle
Scavenger. Your profile history displays a tendency for sarcastic replies. Any chance of changing your tune to encourage others to engage in well mannered sensible discourse?
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Old 1st Apr 2019, 14:14
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Originally Posted by megan View Post
Test pilot of the 707 Tex Johnson quotes a yaw limit of 15 and cites the exceedance as being the cause of the loss of a Braniff 707-220Could have been describing the subsequent loss of the RAAF 707.
Megan,
Which is why I specifically noted ---- post B707 re. sideslip limitations.
The RAAF loss of the 707 was very sad, but also depressingly predictable.
Tootle pip!!
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Old 1st Apr 2019, 16:06
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Thanks, megan, I always wondered what the limit was.
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Old 1st Apr 2019, 16:32
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Read the context where I wrote most instructors still erroneously teach it as just that and get the student to cut the throttle either abeam the downwind end of the runway or on the turn to base leg.
I did not recommend that technique
The RAF did, though! That (at the end of the downwind leg) was exactly how they were taught and flown and possibly still are, certainly in SEP aircraft.
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Old 2nd Apr 2019, 00:59
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Folks,
I am puzzled, where in Australia do I find these "busy" GA airfields where a glide approach would upset traffic flow --- what traffic flow??
Certainly not at YSBK, rarely as YSCN, and not at any airfield with a significant GA component, on the east coast, that I have seen in recent years.
Just a little while ago, driving around the perimeter road at said YSBK, not a single aircraft on the air, I could see a couple of rotating beacons on the ground, although I must admit, last Tuesday I saw three aircraft airborne all at once in the circuit. .
"Back in the day", at (then) ASBK, when twelve or more at one time in the circuit was NOT grounds for comment, glide approaches were no big deal, even when you were four or more abreast on 05/23 grass and runway.
Tootle pip!!

PS: Why did the seatwarmers in Canberra ever agree to Australia giving away A----- for Y??? We don't live in Yustralia?? A bit like regos, North America would never give away N, likewise Great Britain G, France F, Germany D, Italy I, Canada C??

Last edited by LeadSled; 3rd Apr 2019 at 22:33.
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