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John Farley's thoughts on forced approaches

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John Farley's thoughts on forced approaches

Old 17th Nov 2019, 21:17
  #21 (permalink)  
 
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Just to repeat what I said in the obit thread after John passed, there is a section in the Harrier pilot notes that says something along the lines of, "Do not try this <maneuver> unless you are John Farley!" referring to the famous
(fast forward to 33 seconds):
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Old 17th Nov 2019, 22:01
  #22 (permalink)  
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Yes, I remember watching John fly that vertical vertical takeoff at Farnborough in 1982! Happily, he did it well, and everything worked. If it did not, a gliding landing was not going to work, I hope the ejection seat would! Non civil operations may take risks which are unacceptable in the civil, or certified aviation world.
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Old 18th Nov 2019, 01:42
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Originally Posted by Pilot DAR View Post
Non civil operations may take risks which are unacceptable in the civil, or certified aviation world.
Just another day at the office for a Test Pilot. They find and define the parameters under which us mere mortals fly, (and conduct Forced Landings).

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Old 18th Nov 2019, 04:18
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His autobiography “A View From The Hover” is a must read.
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Old 18th Nov 2019, 10:00
  #25 (permalink)  
 
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Originally Posted by tcasblue View Post
Appreciate the comments about JF but seeing as the thread is about gliding technique after a power loss, I will try to get it back on track and hopefully we can keep it there.

I re recently read an article about power loss in high drag aircraft in the ultralight world where they have relatively small inertia compared to the jets or the C182 on floats. The link is here.....

https://electricmotorglider.com/2018...energy_part-2/

There seems to be difficulty picking up speed and potentially stalling if the flare is too early. Any opinions on this article or related info would be welcome.
With reference to the attachement, I'm struggling to understand how the drag coefficient for the Schweizer 2-33 type glider and the Cessna 172 (if that is what they are) with all their lumps and bumps, can be less than that of the NACA 0015 type aerofoil at 0?
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Old 18th Nov 2019, 15:14
  #26 (permalink)  
 
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Originally Posted by longer ron View Post
Most of us actually read the thread title TCAS = John Farley's thoughts on forced approaches
Correct....thoughts on forced approaches. And I am sure if any of us were having a discussion with him about forced approaches, he would be much more interested in your opinion on forced approaches instead of hearing well deserved accolades.

Originally Posted by Pilot DAR View Post
This is why I train, as John's passage later validated for me, to store extra speed in a glide. Unless you need to stretch your glide to make it to the coast, or over the mountains, choose a spot closer, make no attempt to stretch the glide, and get it down well. With the extra speed stored, you can either spend it to prefect your flare, or dump it out at the last minute as a sideslip, or more flap extension. 'Worst is you land long. 'Better than landing short on a forced landing!
The information provided by Farley is interesting but I believe that it is directed more towards single engine jets with high wing loading rather than your typical single engine general aviation aircraft. I base this statement on mention of a 30 to 40 degree nose-down pitch. I have not read his book(please no harsh statements, I just finished one of three Winkle books I have).

So the question is..... is this applicable(or somewhat applicable) to a typical single engine piston trainer. His statement(from your quote) appears to me to be a consideration for flare capability which is why I posted that link to the article about high drag ultralights which appears to have the same issue, possibly for different reasons.

Obviously, each forced approach(Americans use a different term) is a different situation. Extra airspeed during the glide can set up a situation where one has wasted their energy. One could have a field in sight fairly close and chosen it over a further away field and then subsequently discovered that their first choice is unusable but they wasted their energy and the second choice is now too far. Be careful when giving away energy unless you are sure that you will never wish that you had it back again.

Landing short is not always worse than landing long, it just depends on the situation although it does increase the likelihood of the instinct to get very slow while stretching the glide to enter the picture. My personal preference in an engine out forced approach scenario where one has a somewhat marginal but reasonable field to use and not much else with typical damaging stuff at both ends of the field is to be close to the appropriate glide speed with some extra energy carried onto short final in terms of a bit too much altitude. I do this by targeting a flare point 1/3 down the relatively short runway while on-speed.

The reality is that the average pilot has a good chance of not being in the perfect position when approaching short final and will either be a bit high or a bit low(if you are grossly high or low, then you screwed it up and are on your own). We know stretching the glide has large risks in terms of a stall so being low is best avoided whereas being on speed and intentionally a bit high allows that sideslip that you mentioned earlier to be used, possibly quite aggressively if aircraft type allows and it can be extremely effective in some types. However, if I end up being slightly off my 1/3 touchdown point I will be targeting close to the threshold allowing the normal approach speed to still work.

Bottom line....perfect setup is best, sideslip is good, stretching glide is bad. The superpilots do the first one. Average guys like me are capable of the second and occasionally end up doing the unintentionally doing the first. Superpilot wannabe's frequently end up doing the last.

Last edited by tcasblue; 27th Nov 2019 at 20:18.
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Old 18th Nov 2019, 17:56
  #27 (permalink)  
 
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Alternate Fields?

Having put various gliders into a number of fields, I haven't bothered with alternate fields. Those were winnowed out on the way down from 2000' to 1000'. Below 1000' is where surface irregularities become more readily apparent, but you likely no longer have safe reach to an alternate

The drill becomes picking out the best spot to touch down on.
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Old 20th Nov 2019, 19:31
  #28 (permalink)  
 
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Some good stuff in this thread, contrasting all sorts of different aircraft which may have a low glide ratio -- some military jets, parachutes, lifting bodies, Space Shuttles, ultralights / microlights, helicopters autorotating.

The idea of keeping speed in reserve also works for wingsuit BASE jumpers. They certainly don't want to be at best glide when having to cross obstacles while terrain following. They want to have lift / energy in reserve to pull up (relative to their existing flight path) in case they misjudge their flight path.

Sometimes using all the glide possible is what is needed to get to a good landing spot, while other times carrying extra energy down onto final will give one more options to stretch the glide or scrub energy off with a sideslip. Sometimes I suppose one might shift between multiple strategies -- One could start with lowest rate of descent glide while searching for a good landing spot, go to best glide to get towards the chosen field (modified as needed for wind to optimize the polar over the ground), then carry some extra speed on final approach until certain that one hasn't undershot.

Although it is just one of the types of aircraft mentioned in the thread, I looked up more on the NASA lifting bodies. A couple of them flew approaches at about 280-300kts and touching down at 180-200kts -- thus carrying about 50% more speed on final approach than for touchdown, which should qualify as carrying extra speed into the flare. Some of these 'gliders' had rockets available to assist in the landing, to keep speed from decaying as quickly, allowing more time to get the flare right. [Ref.: Testing Lifting Bodies at Edwards by Robert Hoey]
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Old 21st Nov 2019, 04:34
  #29 (permalink)  
 
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Constant Aspect Approach

I believe most glider pilots adopt the concept of the Constant Aspect Approach, it having been drilled into them in circuit planning pre-solo in glider pilot training. Keeping the landing zone at a constant angle of view whilst setting up for the approach is fundamental to achieving a landing in the correct part of the field.
There are videos and further explanations on gurgle...
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Old 21st Nov 2019, 08:16
  #30 (permalink)  
 
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Correct about the constant aspect approach with a glider, and also we carry extra energy with a speed significantly higher than best glide. Typical best glide speed for a modern glider is around 80 kph, aand approach 100 kph, though this will vary according to local conditions. It's a lot easier to land in a field with a glider than with an aircraft minus the use of engine though, airbrakes are a very powerful tool for approach management. Add landing flap to this, and we can touch down with great precision. A few gliders also have a tail parachute, but this is not common. It does shorten a landing run, but requires a lot of skill and judgement to stream if you intend to use it on final approach. We don't usually need to sideslip except in a few vintage types.
The aim is to set up an approach using half airbrake, which allows a reduction of brake if landing short, until back on the glide path, or more brake if landing long. If the glider has landing flaps then one normally sets them on the downwind leg then leaves them alone. Full airbrake in the hold off will shorten the float
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Old 27th Nov 2019, 04:11
  #31 (permalink)  
 
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Originally Posted by chevvron View Post
Years later, I experienced gliding in a Hunter T7.
I was up with the late lightningmate, (not to be confused with Lightning Mate who is still with is on this forum) one of Farnborough's ace test pilots. He pulled the throttle at about 16,000ft just south west of Greenham Common and asked Boscombe for a '1 in 1' to their main runway. Pullng the speed back to 250 kt indicated gave rod of 500ft/mile. Boscombe vectored us towards their centreline giving us range from touchdown checks and when our height numerically equalled range eg 11,000ft at 11nm, he dropped flaps and gear and increased rod to 1,000ft/mile (1 in 1, get it?) and we continued at this rate of descent until it was time to flare for a touch and go.
Chevvron,
If I may make a few technical corrections to what you have said (and lightningmate was a good friend and colleague of mine): The normal gliding speed in the Hunter with undercarriage and flaps up was (and still is!) 210 KIAS which gave a range of 2nm/1000 ft altitude loss (4.7 deg glide angle). For practise, 2 notches of flap (23 deg) was lowered and 5500 RPM set (in a T Mk7) to simulate windmilling engine drag. When the '1 in 1' slope was intercepted (1nm/1000 ft, 9.34 deg glide angle) the undercarriage was lowered and 210 KIAS maintained by lowering the nose. Airspeed was then varied between 180 and 240 KIAS to maintain the '1 in 1' slope. At a visually judged point (typically between 500 and 1000 ft above touchdown) the flaps were lowered fully to reduce speed to 170 KIAS for commencing the flare. If it was a practise the power would be reduced at the flare to 4500 RPM (to protect the engine surge margins for the tough-and-go or go-around and maintain a short engine spool up time).

This pattern worked because of the drag characteristics of the Hunter with the undercarriage down at 210 KIAS. It was initially used also in the Hawk T1 when it entered service and it worked with idling thrust but would not with windmilling drag, and hence the radar forced landing pattern was developed. This pattern will work with any drag polar so can be used on most types.

Returning to where this thread started, if a high drag aircraft is gliding with a steep angle then a given angular change of glide angle will equate to a smaller distance over the ground than for a low drag aircraft with a shallower glide angle. Therefore, it is easier to judge the touchdown point in a high drag aircraft. However, the probability of not having sufficient energy to make an airfield following an engine failure is greater with high drag.
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Old 27th Nov 2019, 17:23
  #32 (permalink)  
 
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Originally Posted by Piper.Classique View Post
Correct about the constant aspect approach with a glider, and also we carry extra energy with a speed significantly higher than best glide. Typical best glide speed for a modern glider is around 80 kph, aand approach 100 kph, though this will vary according to local conditions. It's a lot easier to land in a field with a glider than with an aircraft minus the use of engine though, airbrakes are a very powerful tool for approach management. Add landing flap to this, and we can touch down with great precision. A few gliders also have a tail parachute, but this is not common. It does shorten a landing run, but requires a lot of skill and judgement to stream if you intend to use it on final approach. We don't usually need to sideslip except in a few vintage types.
The aim is to set up an approach using half airbrake, which allows a reduction of brake if landing short, until back on the glide path, or more brake if landing long. If the glider has landing flaps then one normally sets them on the downwind leg then leaves them alone. Full airbrake in the hold off will shorten the float
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May I beg to disagree?

We teach fairly conventional circuits in gliding (I'm a UK Full Cat Instructor). They look fairly much like power circuits apart from having a diagonal leg joining downwind to base, which allows you to keep the landing area in sight, and means you don't have a far point. It's not the same as the constant aspect approach I'd use for a forced landing in power. The aim is to get to a sensible place on final, then fly towards the airfield until half to two-thirds airbrake is needed for the actual final approach. Also, on lots of gliders setting landing flap is not sensible until wings level on final for a couple of reasons - on some aileron control decreases, and on some the approach angle is pretty steep (there's a reason landing flap on an ASW20 is called 'Jesus Flap'). So it's neutral or slightly positive flap until final, then landing flap.

Paul
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Old 27th Nov 2019, 19:52
  #33 (permalink)  
 
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May I beg to disagree?
of course. It's a discussion forum. I'm an ex glider FI who used to instruct in UK up to 1991, then France.
It seems that techniques differ a little between the two countries. We don't normally use all the available flap for landing, so that's probably same same.
We do use a constant aspect though we don't cut the corner as is now taught in UK, at least not officially. The idea is to set up a half brake approach anywhere between the start of the base leg and the start of the final approach with the glider configured for landing. Personally I like that 45 degree leg. I hope you agree with me that it's a lot easier to put a glider in a field than it is a light aircraft with a dead engine which was the main point of my post.
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Old 27th Nov 2019, 20:18
  #34 (permalink)  
 
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Originally Posted by Piper.Classique View Post
...
I hope you agree with me that it's a lot easier to put a glider in a field than it is a light aircraft with a dead engine which was the main point of my post.
Very definitely. You've got so much more glide performance in a glider that if you don't use the airbrakes you probably won't land on the airfield, even if the rest of the circuit is exactly right. Whereas with a power engine off pattern, there's much less flexibility.

Paul
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Old 28th Nov 2019, 07:26
  #35 (permalink)  
 
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Originally Posted by LOMCEVAK View Post
Chevvron,
If I may make a few technical corrections to what you have said (and lightningmate was a good friend and colleague of mine): The normal gliding speed in the Hunter with undercarriage and flaps up was (and still is!) 210 KIAS which gave a range of 2nm/1000 ft altitude loss (4.7 deg glide angle). For practise, 2 notches of flap (23 deg) was lowered and 5500 RPM set (in a T Mk7) to simulate windmilling engine drag. When the '1 in 1' slope was intercepted (1nm/1000 ft, 9.34 deg glide angle) the undercarriage was lowered and 210 KIAS maintained by lowering the nose. Airspeed was then varied between 180 and 240 KIAS to maintain the '1 in 1' slope. At a visually judged point (typically between 500 and 1000 ft above touchdown) the flaps were lowered fully to reduce speed to 170 KIAS for commencing the flare. If it was a practise the power would be reduced at the flare to 4500 RPM (to protect the engine surge margins for the tough-and-go or go-around and maintain a short engine spool up time).

This pattern worked because of the drag characteristics of the Hunter with the undercarriage down at 210 KIAS. It was initially used also in the Hawk T1 when it entered service and it worked with idling thrust but would not with windmilling drag, and hence the radar forced landing pattern was developed. This pattern will work with any drag polar so can be used on most types.

Returning to where this thread started, if a high drag aircraft is gliding with a steep angle then a given angular change of glide angle will equate to a smaller distance over the ground than for a low drag aircraft with a shallower glide angle. Therefore, it is easier to judge the touchdown point in a high drag aircraft. However, the probability of not having sufficient energy to make an airfield following an engine failure is greater with high drag.
Thanks for correcting me; my excuse is it happened 40 years ago and a few minutes earlier I had experienced my first 'grey out' as we piulled through a loop at 5.5g and I hadn't got a g-suit!!
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Old 28th Nov 2019, 15:56
  #36 (permalink)  
 
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Originally Posted by PaulisHome View Post
May I beg to disagree?
<snip>
Also, on lots of gliders setting landing flap is not sensible until wings level on final for a couple of reasons - on some aileron control decreases, and on some the approach angle is pretty steep (there's a reason landing flap on an ASW20 is called 'Jesus Flap'). So it's neutral or slightly positive flap until final, then landing flap.
Paul
And retracting landing flaps can lead to stalling. There was a fatal accident involving an ASH25 where that was believed to have happened. Not sure if it's in the flight manual for that glider that once set they should be left.
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