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PFL advice

Old 19th Nov 2019, 10:16
  #21 (permalink)  
 
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Originally Posted by Pilot DAR View Post
One of the many wisdoms passed to me repeatedly over the decades has been: Once you have a plan in an emergency, don't change it unless there is no choice. This goes extra for forced approaches. Aside from allowing yourself several different landing sites which are all very close to each other, you're better to make the right decision first, and stick with it. Changing your mind while gliding down certainly wastes altitude, and invites a poor outcome. If there is an adequate landing site close, it's a better choice than the perfect looking one farther along. 'Same logic as not flying past a fuel stop, 'cause you think you can make it.

While enroute, you should be constantly considering where you might force land if the engine quit in the next minute. Perhaps the site is one you just flew over, and had a decent look. The one you've flown over and seen from several angles, is certainly better known to you than the one which is still ahead. You can't judge its suitability and distance as well. If the engine quits, you're no longer trying to get further along your route, you're just trying to get down safely. Making the best decision first, and sticking with it is an important element of things not getting much worse mid emergency. If you're really unsure about the suitability of the forced approach sites in your area, fly higher, to give yourself more time to select, and glide.
Just to be absolutely clear for the original poster, if you are undershooting the field on a forced landing it is no longer a forced landing it is a crash. This is a situation where you need to re-evaluate what’s happening because it is unrecoverable. I do not agree that you doggedly stick with the original decision blindly and hit the ground at high speed short of the intended aiming point. Actually, that’s the point I was making about the original exercise. Both the instructor and the original poster knew the PFL exercise was going wrong and left the decision to bin it too late. That’s the learning point of what you flew. It would have been better to make a different decision while you had more options rather than continue down and select flaps (just because that’s what you do) and put yourselves and the aircraft in a precarious situation.

By the way, the T67 flight manual makes no mention of using flap to for improved glide. It says that you use the flap to adjust the glide to achieve the required touchdown point. It recommend the same speed for clean and the first stage of flap (70kts) and the glide will definitely be degraded by the addition of flap because of the increase drag. Just to explain that a little further - the flap will mean the wing produces a bit more lift but the wing is already generating the same amount of lift as the aircraft mass so when you select the flap you will reduce the angle of attack and keep producing the same amount of total lift. You will definitely be generating a bit more drag. So the glide range will decrease. In some aircraft you may be able to reduce the rate at which the aircraft is descending because you can generate the required lift at a slightly lower speed but you will not go as far over the ground. You may stay in the air slightly longer but will not go as far.




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Old 19th Nov 2019, 11:48
  #22 (permalink)  
 
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To the original poster.

There are no circumstance with a conventional aircraft, where adding even little flap would allow to make the runway which was undershot in clean configuration. I might be wrong, but it seems to me that it is even mentioned in basic Principles Of Flight ground school subject. This is due to the fact that the wings for most aircraft is designed to have the best L/D ratio at the clean configuration, and that is when the aircraft will glide the farthest. Having flaps extended, improves lift, but also changes the drag, and it does not give the same maximum L/D ratio any more, thus the glide steepens. It is possible that there are some airplane designs which incorporate the improvement of L/D ratio when flaps extended, but I suspect it is very hard to land such aircraft, because it will tend to fly at the point when it should stop flying.

To assure myself, I have event taken a Stick And Rudder copy from the shelf, and it's clearly states "Flaps have a double purpose of lowering the airplane's stalling speed and of increasing its drag, thus steepening its glide. As far as glide control is concerned, only this drag effect is important. With flaps down, the airplane's glide is so exceedingly steep that there is hardly any problem of glide control;". Not all are fans of the book, but it just proves that the basic principles exist more than half of century, and I wonder why would anyone suggest otherwise, except proven in practice.

As per the whole situation. I think You had a very good opportunity to learn many things and make conclusions. Your initial feeling was correct, and the Go-Around would have been the right action (You mentioned that You'd have done it if being alone in the cockpit, or with an examiner. I don't think this decision would count as a fail - it is good judgment). The tricky part here is that You were flying with instructor, who is the PIC, and in general, You have to trust him, because he is supposed to "know better". Depending on how long You are in training and how much experience You already have there is a certain degree of psychological influence on the student's decisions because instructor is supposed to mentor/guide the student and demonstrate things. So You got in to the trap of following suggestion of Your instructor, which is the right thing on it's own. You cannot blame Yourself for this. The issue probably was that instructor chose incorrect strategy of demonstrating his point. The ideal course of actions in that situation, IMO, could have been "You call Go-Around and execute it. Instructor accepts it, but tells that the approach could have been executed. On the next circuit instructor takes the controls and demonstrates from the same aircraft position. The exercise is finalized by the 3rd circuit, where You execute it Yourself". This didn't happen, but it doesn't mean it is Your fault in this case. Maybe next time You should call for GA as soon as You feel it and not hesitate. Don't blame Yourself and don't blame anyone, instead learn from it. As Your experience grows, You will realize that instructor wasn't always correct, but it's ok, we are all humans and all make mistakes. You are lucky to realize this now. Since You have posted this situation, and there was a discussion on it, I believe You have debriefed it quite extensively, so next time You will make the right decision.

Don't feel unsettled. This is a good lesson for You, not all have the luck to experience it during the training.

Good luck on Your further training.

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Old 19th Nov 2019, 12:45
  #23 (permalink)  
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Thanks, useful summary of the lessons. I would actually love to do some of these exercises solo, I would probably be more conservative but I think it would be valuable to know that there is no-one to bale me out if I mess it up. Is that permitted/done ? After all, if all goes well in a few weeks, I will be out there alone anyway and I don't want to be afraid to keep working on these key skills.


Originally Posted by s4ex View Post
To the original poster.

There are no circumstance with a conventional aircraft, where adding even little flap would allow to make the runway which was undershot in clean configuration. I might be wrong, but it seems to me that it is even mentioned in basic Principles Of Flight ground school subject.
That was certainly my understanding until this incident, so I was troubled to be told to add some flap when I thought we were about to land crash short, and there was not a snowball's chance in hell of landing too long, which is why I came here for a sanity check!
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Old 20th Nov 2019, 06:31
  #24 (permalink)  
 
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Best glide is with a clean aircraft at best glide speed.
as I recall “longest time in the air glide” is a different speed, but doesn’t fly as far. I can’t remember the second speed as I’m of the view “why would I need that?”.

They are illustrated by best rate of climb and best angle of climb. I couldn’t get my head round them until I imagined best angle as a balloon rising vertically, but slowly.

I’d not go near flap until I was sure of the runway.
There’s no flap involved in best rate of climb.
I think what you describe is a practise dead stick landing on a runway.

A PFL goes down to 50’ over a field somewhere and ends with the phrase “we’d have made that” or “that would have hurt”. It might start as you rejoin the circuit, but I don’t think a PFL involves orbiting while you wait.

At something like ~300’ if it’s not going to work, you need to be telling your instructor what you’d do with no engine, in the early days “crashing” is a valid statement. “I’d try for that bit of grass” or “that taxiway” or some such, (before going around) is, “let’s just bin this and go around” isn’t

My first PFL, I picked a field covered in hay bales, when challenged I said “it doesn’t matter, we’re not actually going to land there”, that took a bit of explaining by my FI, and a change in my mindset.

back to the original question, check best glide in the POH, show your instructor, be thankful for what you learnt. It is training after all.
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Old 20th Nov 2019, 09:26
  #25 (permalink)  
 
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This chap raised the flaps to help a bit https://assets.publishing.service.go...010_G-YMMM.pdf
Page 5 is the relevant part to this thread.
Only time I've done a PFL off airfield for real in a fixed wing was at the bottom when told to climb away the engine didn't respond due to a failed throttle linkage. Subsequent landing was one of my better grass ones! The Odd One put it perfectly, almost straight out of the patter manual.

SND
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Old 20th Nov 2019, 09:28
  #26 (permalink)  
 
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Originally Posted by kghjfg View Post
...
as I recall “longest time in the air glide” is a different speed, but doesn’t fly as far. I can’t remember the second speed as I’m of the view “why would I need that?”.
...
A little careless attitude, IMO. Not always One needs to glide far. The crash-landing place can be just near by, but it will be useful to have as much time as possible to "Declare Emergency, Secure the engine, unlatch the doors, and make any other preparations for the crash". Being at high altitude, One wouldn't want to be descending at high RoD while attempting to restart the engine.


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Old 20th Nov 2019, 10:27
  #27 (permalink)  
 
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Originally Posted by s4ex View Post
A little careless attitude, IMO. Not always One needs to glide far. The crash-landing place can be just near by, but it will be useful to have as much time as possible to "Declare Emergency, Secure the engine, unlatch the doors, and make any other preparations for the crash". Being at high altitude, One wouldn't want to be descending at high RoD while attempting to restart the engine.
good call, I should be more aware of that as well for that reason.
(Off to check the POH.)
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Old 20th Nov 2019, 12:16
  #28 (permalink)  
 
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Hi

Don't think I was suggesting use flap to extend glide.

But have reduced flap to regain our aiming point if that flap was selected prematurely

Some posters are adamant once selected no reduction . why ?

Rgds

PS Do we have to always to unthinking follow POH eg the PA34 poh describes a short field t/o that has you slower than Vmca in event of eng. failure Just a thought
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Old 20th Nov 2019, 13:04
  #29 (permalink)  
 
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Originally Posted by kghjfg View Post


good call, I should be more aware of that as well for that reason.
(Off to check the POH.)
I would have a look at the difference it makes - I doubt its more than a few seconds from a normal cruising altitude. Flying the aeroplane is crucial in the event of the failure of your only powerplant. I would be far more focussed on flying the aeroplane towards a sucessful landing site than anything else. You are likely to waste those few seconds you save trying to nail the 65kts you need for minimum sink with a stage of flap than you are just concentrating on flying the plane. If you want to get maximum glide performance try to slow down enough to stop the prop windmilling (if it still is). I soared a super cub in wave in Scotland once and stopping the prop gave an extra 250 fpm climb rate so that was fairly significant. It also rules out the random cough and short lived restart that will ruin your day if it happens at 100 feet...

On the subject of Vx and Vy.. I have heard so much rubbish talked about the difference between best rate and best angle of climb. If you are ever in the situation where climbing at Vx compared to Vy means you will miss an obstacle rather than hit it just go and have a cup of tea and consider the wisdom of taking off.. Its interesting from a techincal point of view and totally pointless from the point of view of conducting a sensible flight.
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Old 20th Nov 2019, 13:09
  #30 (permalink)  
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But have reduced flap to regain our aiming point if that flap was selected prematurely

Some posters are adamant once selected no reduction . why ?
a): Because nothing in the flight manual/POH says this is acceptable, b): the take away lesson is that if you could have to retract them, you should have already known not to extend them, c): I have never found that there is any power off performance benefit from retracting flaps. What you will lose settling as the flaps retract, you will not recover later with the lesser drag. You're just spending glide altitude for nothing. If you have the altitude to waste ('cause you've chosen a close field), you won't need to retract the flaps to improve the glide.

PS Do we have to always to unthinking follow POH eg the PA34 poh describes a short field t/o that has you slower than Vmca in event of eng. failure Just a thought
No need to untihink the POH, just fly the plane the way the manufacturer has stated, and the certifying authority has approved. After the accident, it's hard to tell the investigator and insurer that you thought you knew more than the aircraft manufacturer and approving authority, so decided to do it your way!

Vmca is the speed below which controlled single engined flight is not assured. You can fly the plane slower than this speed if you choose, and a short field takeoff will probably require this in some types. You just have to notice that if, during this phase of flying, you loose an engine, it may be a good decision to gently close the other throttle and force land ahead, as though it is a single engine plane, 'cause it's not going to fly like a twin on one!

There are many more layers of experienced thought, and approving authority review in flight manuals/POHs than just the thinking of the pilot that day. if you want to operate outside their recommended practices, you would be wise to have your alternate procedure approved. I have done this many of times - preparing, and having approved, a flight manual supplement, to describe the changed operation and limitations. This is a reminded to pilots to also read any FMS which is appended to the flight manual for the plane they are flying.
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Old 27th Nov 2019, 18:21
  #31 (permalink)  
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Hi again!

I thought I might revive this thread to give feedback on the PFL I was asked to do for my GFT. Starting from 2,000' above the airfield I was asked to land without engine. I felt it went beautifully, I played it conservatively, keeping a good bit of spare altitude, progressively going to 20 degrees of flap as I approached the threshold and then 40 degrees when it was in the bag. I landed perhaps 300 feet beyond the numbers on a 5,500' runway.

During the debrief the examiner criticized me for wasting runway. He said that on a real forced landing in the bush, I will almost never have spare space so I should be demonstrating a precise touchdown as early as reasonably possible. I said that was true, but we weren't in the bush, we were landing on a 5,500' runway so I felt it was right to allow a generous margin for error. He accepted that, but said that the point of the exercise was to demonstrate that I could do it for real.

It was a very amicable discussion, he completely accepted my argument, but it was an interesting difference in understanding of the purpose of the exercise; I was playing the hand I was dealt, he was asking me to demonstrate how I would have played a different hand!
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Old 28th Nov 2019, 11:38
  #32 (permalink)  
 
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Interesting Double Barrel, it sounds like you flew the exercise nicely as briefed. The rub seems to be the way it was briefed.

My thinking is that if the instructor/examiner wanted you to land as close to the near hedge as possible then he should have made that clear. His argument is perfectly valid - excpet that's not what he asked you to demonstrate.
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Old 28th Nov 2019, 12:58
  #33 (permalink)  
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so I felt it was right to allow a generous margin for error.
Good job DB, you're right, minimize risk with good judgement. You can help yourself in this theme next time by stating, and then aiming for, a distinct feature a little bit down the runway. The piano keys are an example. "My planned touchdown point will be the far end of the piano keys", which will what you will then be judged on, and... you'll earn a point for thinking about keeping practices appropriately safe, which still demonstrating the objective.

If the engine actually sputtered during a misjudged gliding approach, and you had been aiming at the exact hedge, you went through it for no good reason for a practice exercise.
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Old 28th Nov 2019, 15:05
  #34 (permalink)  
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Originally Posted by Pilot DAR View Post
.... You can help yourself in this theme next time by stating, and then aiming for, a distinct feature a little bit down the runway. The piano keys are an example. "My planned touchdown point will be the far end of the piano keys", which will what you will then be judged on, and... you'll earn a point for thinking about keeping practices appropriately safe, which still demonstrating the objective.
You are right, that would have been the perfect way to handle it. Next time!
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Old 30th Nov 2019, 02:07
  #35 (permalink)  
 
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The most important but most neglected part of forced approach training IMO is the cause check. A review of the accident record shows that up to 80 % of engine failures are caused by the actions or inaction's of the pilot. Some of these are not recoverable (eg running out of gas) but in many cases power can be restored by prompt effective action of the pilot (eg switching fuel tanks). Flight training does a disservice to students because the emphasis on flying the maneuver to get a good score on the flight test diminishes the importance of training to minimize the possibility of the engine failing in the first place or if it does fail, immediately recovering engine power

The accident statistics also hint that for every full engine failure there are probably at least 2 partial engine failures. This is never taught at flight schools but the decision making for a partial engine failure is a lot harder than for a full engine failure

Finally the condition of the field is the least important think to worry about in a forced landing. If the engine fails the insurance company just bought your airplane. Your only job as a pilot is to get the airplane down without hurting anybody, the condition of the aircraft afterwards is irrelevant. Therefore field selection criteria are in order of importance: be close, have the minimum amount of obstacles on approach, and be reasonably flat.
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Old 30th Nov 2019, 08:01
  #36 (permalink)  
 
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The accident statistics also hint that for every full engine failure there are probably at least 2 partial engine failures. This is never taught at flight schools but the decision making for a partial engine failure is a lot harder than for a full engine failure
They do indeed, and in the UK, the outcome from a partial failure is usually a lot worse than the total failure.
We certainly do teach partial failure drill. The first question for the student is 'how can you tell you've a partial failure?' The answer I'm looking for is 'loss of altitude'. This generally places one in a worse position than a total failure. We teach levelling off at whgatever power is available. If it is at or above the minimum safe manoeuvring speed, then provided terrain is OK, continue to nearest suitable airfield, looking for landing ground along the way. Once secured, then look for a reason, change tank, pump on, carb ht etc. One of my favourites is the primer, it's happened to me and air leaking by an open primer can seriously affect the power output.
I generally, then turn it into a total failure.
In the classic sudden total failure training, we teach
1. Best glide
2. Pick a field, fly circuit to this field.
3. Look for failure. I like to work left to right in the PA28, as fuel is the most common cause.
4. No failure found, MAYDAY, brief pax
5. On final for the field, once any electric flap setting complete, master off, mixture ICO, fuel off, door open etc.

Historically in the UK, there have been failures caused by pax interference 'I wonder what this red knob does?' In a recent case, a pilot admitted knocking the mags off with their knee! In another case, 2 PPLs crashed downwind running out of fuel with 2 hours remaining in the other tank...

The complete course is 45 hours. You can't possibly bring the average student to a high state of competence in that time in all aspects, so we can only do our best to cover everything. The Club environment helps I think for students to mix with PPLs and get more out of chatting with other people more experienced.

TOO
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Old 30th Nov 2019, 09:37
  #37 (permalink)  
 
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Having had a partial myself, as an inexperienced instructor over twenty years ago, I always put a simulated partial in any check flight, LPC or initial test, I'm now about to send a note to remind all my instructors not to forget to include training for such!

TOO
I too put it just before the "total" failure!
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Old 30th Nov 2019, 10:56
  #38 (permalink)  
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I think I was well taught how and when to attempt a restart, although of course they always fail to restart during training! I'm not sure how that could be safely practiced except in a simulator ?

But it's true that a partial fail was not discussed during my training. This did come-up on PPRuNe while ago and forfoxake posted this with a link to this booklet which I found interesting.
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Old 30th Nov 2019, 10:57
  #39 (permalink)  
 
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My philosophy regarding engine failures/loss of power, total or partial, is that there are 4 potential causes: mechanical, fuel, ignition, icing. If a pilot mis-selection, inadvertent or otherwise, has been made then it typically falls under fuel or ignition. If this philosophy is taught clearly then it applies to all piston engine aircraft and only the detail of how to analyse and potentially correct the cause needs to be taught for the type being flown.

The other generic aspect to consider is with a variable pitch propeller: leave it as set/fine if a restart is to be attempted, select coarse if the engine is to remain shut down.

I am not involved in PPL level instruction so I would be interested to know if these philosophies are taught at this level and if it is considered reasonable for an ab initio student to have the capacity to to think them through.
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Old 30th Nov 2019, 17:35
  #40 (permalink)  
 
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Most GA training aircraft have fixed pitched props but I have done 3 PPL’s on aircraft with vp props. For those aircraft I add prop full coarse (low RPM) as part of the engine shutdown flow.

Also in a retractable gear aircraft I teach that all forced approaches not to runways will be performed gear up.
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