EFATO
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All of this debate is theoretical.
Almost impossible to teach (at least to PPL students or low-hour private pilots) and entirely dependent on the nerve strength of both the instructor and the student. Doing 45+ degree banked turns below 500ft will scare the hell out most pilots (instructors included) even if a well researched paper predicts a favorable outcome of the maneuver. Training this procedure at a safe altitude (or in a simulator) will not help at all, because all the human factors that make it so difficult in real life will be taken away.
I would rather opt for a software solution (like an app for a smartphone or iPad) that will emit a signal once a speed/position/altitude has been reached, from which an averagely skilled and trained pilot should be able to fly a successful return maneuver within the normal operating envelope of his aeroplane (best glide speed +/- 10kt, turns with no more than 30 degrees of bank, ample reaction times). If your device hasn't beeped yet, you glide to a landing straight ahead, if you heard it beep, you are safe to turn back.
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n5296s, the input was very useful. Though in real life I guess the prop might be windmilling?
Thanks also to Big Pistons Forever, I have seldom seen such concentrated common sense, especially "under fire".
It seems to me, (by no means a "Sky God"), that I wouldn't even consider the turn back under 500 ft in a C172 or similar, by which time I'm typically turning onto cross-wind, or even earlier for noise abatement etc, as somebody else posted.
So could we perhaps tone down the "Health and Safety" warnings a little if we re-cast the question as "what best to do with Engine Failure On Crosswind?" (EFOC?)
What we generally need to know is how much turning an average pilot can squeeze into any given height, especially if much draggier than usual because of a windmilling prop.
Just my 2c.
Thanks also to Big Pistons Forever, I have seldom seen such concentrated common sense, especially "under fire".
It seems to me, (by no means a "Sky God"), that I wouldn't even consider the turn back under 500 ft in a C172 or similar, by which time I'm typically turning onto cross-wind, or even earlier for noise abatement etc, as somebody else posted.
So could we perhaps tone down the "Health and Safety" warnings a little if we re-cast the question as "what best to do with Engine Failure On Crosswind?" (EFOC?)
What we generally need to know is how much turning an average pilot can squeeze into any given height, especially if much draggier than usual because of a windmilling prop.
Just my 2c.
I would rather opt for a software solution (like an app for a smartphone or iPad) that will emit a signal once a speed/position/altitude has been reached, from which an averagely skilled and trained pilot should be able to fly a successful return maneuver within the normal operating envelope of his aeroplane (best glide speed +/- 10kt, turns with no more than 30 degrees of bank, ample reaction times). If your device hasn't beeped yet, you glide to a landing straight ahead, if you heard it beep, you are safe to turn back.
There are four main reasons to do the research in my opinion, which for me are:-
(1) It'll be fun and interesting
(2) It'll give people who might consider a turnback a clear indicator of when NOT to consider it.
(3) There are lots of runways without a land ahead option. Runway 23 at Lee on Solent, runway 19 at Oban, runway 29 at Sheffield City, Grand Canyon Airport in Arizona, plenty of small island airports or mountain airports around the world. Nobody's going to close these runways - so if they're going to get used, perhaps pilots flying there should have some material they can use for training and practicing turnbacks.
(4) See (1).
G
n5296s, the input was very useful. Though in real life I guess the prop might be windmilling?
Thanks also to Big Pistons Forever, I have seldom seen such concentrated common sense, especially "under fire".
It seems to me, (by no means a "Sky God"), that I wouldn't even consider the turn back under 500 ft in a C172 or similar, by which time I'm typically turning onto cross-wind, or even earlier for noise abatement etc, as somebody else posted.
So could we perhaps tone down the "Health and Safety" warnings a little if we re-cast the question as "what best to do with Engine Failure On Crosswind?" (EFOC?)
What we generally need to know is how much turning an average pilot can squeeze into any given height, especially if much draggier than usual because of a windmilling prop.
Just my 2c.
Thanks also to Big Pistons Forever, I have seldom seen such concentrated common sense, especially "under fire".
It seems to me, (by no means a "Sky God"), that I wouldn't even consider the turn back under 500 ft in a C172 or similar, by which time I'm typically turning onto cross-wind, or even earlier for noise abatement etc, as somebody else posted.
So could we perhaps tone down the "Health and Safety" warnings a little if we re-cast the question as "what best to do with Engine Failure On Crosswind?" (EFOC?)
What we generally need to know is how much turning an average pilot can squeeze into any given height, especially if much draggier than usual because of a windmilling prop.
Just my 2c.
Though in real life I guess the prop might be windmilling
Of course if you have a fixed prop this is all irrelevant.
True. But if you had the presence of mind it would be windmilling in coarse pitch (assuming a constant speed prop). I'd LIKE to compare the difference between a prop windmiling in coarse pitch and one under idle power in fine pitch, but that's beyond my nerve/stupidity. I always do power-off exercises in fine pitch hoping that the two will balance out, more or less.
Of course if you have a fixed prop this is all irrelevant.
Of course if you have a fixed prop this is all irrelevant.
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Interesting experiments.......I might go and try some of my own.
I read a very good article once about EFATO. It was written by some really experienced aerobatic pilot (I forget where I read it, US AOPA I think), and the best bit of advice he gave was "push until the ground fills a two thirds of your windscreen". This is very good advice, as we had an EFATO recently from our airfield (below 500') and as is common the aeroplane stalled. Luckily for the pilot he was not that high but he still managed to end up mushing down and cartwheeling along the airfield as the wing dropped and "landed" first, and he was trapped underneath in a fuel loaded smashed up aeroplane. Hurt but not too seriously but covered from head to toe in avgas.
My buddy was there and sent me some pics, very scary stuff. Luckily all his holes didn't line up that day.....a bit higher, a bit faster, and I expect there would have been a different result.
Whatever you do, keep flying
I read a very good article once about EFATO. It was written by some really experienced aerobatic pilot (I forget where I read it, US AOPA I think), and the best bit of advice he gave was "push until the ground fills a two thirds of your windscreen". This is very good advice, as we had an EFATO recently from our airfield (below 500') and as is common the aeroplane stalled. Luckily for the pilot he was not that high but he still managed to end up mushing down and cartwheeling along the airfield as the wing dropped and "landed" first, and he was trapped underneath in a fuel loaded smashed up aeroplane. Hurt but not too seriously but covered from head to toe in avgas.
My buddy was there and sent me some pics, very scary stuff. Luckily all his holes didn't line up that day.....a bit higher, a bit faster, and I expect there would have been a different result.
Whatever you do, keep flying
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I suspect that may be possible, or (me being a bit of a technological luddite) possibly a graph for any given aeroplane which can be referred to before take-off and says for runway length X and headwind Y in this aeroplane, below height Z you will not get away with a turnback, but above that you have a fighting chance if flown well enough.
G - Yes a good theoretical experiment, that may yield some interesting and anecdotal information reference said aeroplane. But that is the point, it will be that particular aeroplane, with a particular weight, with a particular configuration. The concern Backpacker was alluding to, correct me if I am wrong BP, was that someone MAY, read this, and think, I am going to try that next time I take off in my PA28 or whatever, and guess what - the 45 degree bank angle et al might not work.
This is Bonanza specific. You fly landing approaches at 1.3 times stall speed (good compromise between low speed and safety margin above stall. Therefore in a 45 degree bank angle, multiply the stall speed by 1.3 and you get a turnback speed with same safety margin for stall - app Vy.
Also, which I do not think anyone has pointed out yet, high density altitude airfields make this almost impossible because the climb gradient is flatter, and high weight also reduces climb gradient which in turn raises your stall speed, and turn speed, which increases your turn radius and decrease your rate off turn.
Let your watchward be take care.
G - Yes a good theoretical experiment, that may yield some interesting and anecdotal information reference said aeroplane. But that is the point, it will be that particular aeroplane, with a particular weight, with a particular configuration. The concern Backpacker was alluding to, correct me if I am wrong BP, was that someone MAY, read this, and think, I am going to try that next time I take off in my PA28 or whatever, and guess what - the 45 degree bank angle et al might not work.
This is Bonanza specific. You fly landing approaches at 1.3 times stall speed (good compromise between low speed and safety margin above stall. Therefore in a 45 degree bank angle, multiply the stall speed by 1.3 and you get a turnback speed with same safety margin for stall - app Vy.
Also, which I do not think anyone has pointed out yet, high density altitude airfields make this almost impossible because the climb gradient is flatter, and high weight also reduces climb gradient which in turn raises your stall speed, and turn speed, which increases your turn radius and decrease your rate off turn.
Let your watchward be take care.
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Well, I guess the process is no different than trying to create a graph for, let's say, landing distance. You first figure out what the proper and achievable technique is. You then figure out the baseline results for ISA conditions, MTOW, nil wind etc. And from there you start figuring out what sort of difference different conditions make.
Having seen, and worked with the landing distance graphs in the PA28 POH, I am convinced that it should not be beyond the average PPL to use a more or less similar multi-step graph to figure out the turnback height. But you are right: That graph will be aircraft-specific. Although the research may yield some generic results that would make it easy to adapt the graphs to different aircraft.
And I would not be surprised if the eventual graph contained a "here be dragons" area or something like that. Meaning: Do not go here or there's absolutely no way out. Don't single engine helicopters not have a similar graph for that part of the flight envelope where you cannot survive an engine out (because you're too low and slow for autorotation, but high enough to end up dead)? Pilot training should then simply be about risk mitigation and avoidance of those circumstances.
Having seen, and worked with the landing distance graphs in the PA28 POH, I am convinced that it should not be beyond the average PPL to use a more or less similar multi-step graph to figure out the turnback height. But you are right: That graph will be aircraft-specific. Although the research may yield some generic results that would make it easy to adapt the graphs to different aircraft.
And I would not be surprised if the eventual graph contained a "here be dragons" area or something like that. Meaning: Do not go here or there's absolutely no way out. Don't single engine helicopters not have a similar graph for that part of the flight envelope where you cannot survive an engine out (because you're too low and slow for autorotation, but high enough to end up dead)? Pilot training should then simply be about risk mitigation and avoidance of those circumstances.
Well, I guess the process is no different than trying to create a graph for, let's say, landing distance. You first figure out what the proper and achievable technique is. You then figure out the baseline results for ISA conditions, MTOW, nil wind etc. And from there you start figuring out what sort of difference different conditions make.
Having seen, and worked with the landing distance graphs in the PA28 POH, I am convinced that it should not be beyond the average PPL to use a more or less similar multi-step graph to figure out the turnback height. But you are right: That graph will be aircraft-specific. Although the research may yield some generic results that would make it easy to adapt the graphs to different aircraft.
And I would not be surprised if the eventual graph contained a "here be dragons" area or something like that. Meaning: Do not go here or there's absolutely no way out. Don't single engine helicopters not have a similar graph for that part of the flight envelope where you cannot survive an engine out (because you're too low and slow for autorotation, but high enough to end up dead)? Pilot training should then simply be about risk mitigation and avoidance of those circumstances.
Having seen, and worked with the landing distance graphs in the PA28 POH, I am convinced that it should not be beyond the average PPL to use a more or less similar multi-step graph to figure out the turnback height. But you are right: That graph will be aircraft-specific. Although the research may yield some generic results that would make it easy to adapt the graphs to different aircraft.
And I would not be surprised if the eventual graph contained a "here be dragons" area or something like that. Meaning: Do not go here or there's absolutely no way out. Don't single engine helicopters not have a similar graph for that part of the flight envelope where you cannot survive an engine out (because you're too low and slow for autorotation, but high enough to end up dead)? Pilot training should then simply be about risk mitigation and avoidance of those circumstances.
Risk mitigation is fine but if you want to be holistics about mitigating the risk then you should mitigate the risks for the whole flight. Instead of obsessing about the Turn back between 400 feet and 1000 feet I think the time and energy should be spent on other areas which experience has shown is much more likely to present a risk to a flight like
-practicing the very late overshoot, or
-short field takeoff and landings including a practical stratagy for determining a go no go point, or
-practicing the 180 degree turn on instruments that you would use on an inadvertant IMC encounter, or
-determinimg exactly what your cruise fuel burn with a series of planned test flights etc etc..........
obsessing about the Turn back
Don't single engine helicopters not have a similar graph for that part of the flight envelope where you cannot survive an engine out
Different topic: over on the Cessna Pilots Association, there was some discussion about how trim plays into all this. As in, you're 15-20 degrees nose up at Vy, and the engine stops. Suppose you just let go of all the controls. What happens? Some time soon, the plane will be flying at Vy (assuming you were trimmed in the first place). It may have lost a bit of altitude getting there, but it won't be stalled. I'll give this a try next time I get a chance.
I still don't really see how you get a real developed stall doing this, except maybe trying to arrest the descent close to the runway. I was actually surprised at how benign things were pulling back below stall speed in a descending turn. But clearly people do :-(
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Different topic: over on the Cessna Pilots Association, there was some discussion about how trim plays into all this. As in, you're 15-20 degrees nose up at Vy, and the engine stops. Suppose you just let go of all the controls. What happens? Some time soon, the plane will be flying at Vy (assuming you were trimmed in the first place). It may have lost a bit of altitude getting there, but it won't be stalled. I'll give this a try next time I get a chance.
I see two issues here though.
First is that people are taught to fly by attitude, and by looking out the window, not by chasing the needles. Especially early in their career, VFR. So they will not let go of the controls but intuitively try to keep the nose up, until they realize what happens. But by then it may be too late.
Second is that even if you let go of the controls, there will be a lot of inertia in the aircraft, and it will take a while to settle in a stable glide (again at Vy, assuming it was trimmed for Vy in the first place). During that period there may well be speed excursions below Vy, and even below Vs, but these, I would imagine, will be at a load factor lower than 1G. I would be very, very surprised if the aircraft were actually to stall in this scenario.
Anyway, the point being that the oscillations before reaching a stable Vy descent may take too long. If you fly the maneuver instead of letting go of the controls you reach that stable state much earlier, and have much more opportunity (read height) to figure out what to do next (whatever that may be).
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Okay, I've got the plane reserved for Saturday morning. The weather looks good and I'm keen to explore some of the EFATO turnback issues discussed here.
Please critique my "test plan".
Key numbers from the POH:
Vs = 63 knots (at MTOW)
Vbg = 78 knots (at MTOW) - supposedly yields a 1 in 8.7 glide ratio, and a V/S of ~900 ft/min (to confirm)
Vs in a 45 degree stable descending turn is thus theoretically ~75 knots. Close enough to Vbg to not need to explore the difference in performance between pulling to the stall at 45 degrees, and flying Vbg at 45 degrees. In fact (but to be confirmed) I expect the stall warner to sound continuously, with noticeable buffet, in a 45 degree Vbg stable turn.
Preliminary actions:
HASELL
(i) From height, establish the aircraft in a Vbg stable, trimmed descent. Mark attitude with some sticky tape on the canopy. Write down/time V/S.
(ii) From height, establish the aircraft in a Vbg stable, trimmed descent at 45 degree bank left and right. Mark attitude again with some sticky tape. Write down/time V/S.
(iii) From height, establish the aircraft in a Vbg stable, trimmed descent with the mixture closed. Write down/time V/S.
(i) and (ii) are so that the proper attitude for the subsequent tests can be set quickly. (iii) is to provide data on the difference between throttle closed and mixture closed (prop windmilling), so that all subsequent data points can be corrected for that.
Test items:
All items start from a stable, properly trimmed Vy climb along a line feature, into the wind as far as possible. When passing through a certain safe height (3000' most likely, weather permitting) I'm going to pull the power and:
a. Hold the nose up to see how long it takes for the aircraft to stall. Then recover the stall and see how much time/altitude I lose before in a stable Vbg glide.
b. Hold the stick in the same position, furthermore as in (a).
c. Completely release the stick, let the aircraft sort itself out, furthermore as in (a).
d. Fly the aircraft in a half-G pushover, furthermore as in (a).
e. Fly the aircraft in a ballistic arc (zero G), furthermore as in (a).
(a)-(e) are essentially to see how much "oh ****" time I've got, and how important ingrained reflexes are. If, for instance, (a) delivers the same as (d)/(e) (which I don't expect), the "oh ****" factor isn't all that important.
Subsequent tests include one second of "oh ****" time after closing the throttle, then:
f. Establish Vbg according to the best technique from (a)-(e), then turn into the crosswind 225 degrees at 45 degree bank, turn the other way 45 degrees at 45 degree bank.
g. Same as (e) but with 60 degree bank
h. Same as (e) but with 30 degree bank
(g) and (h) essentially to confirm Rogers
i. Like (f) but start with a left turn 45 degrees away from the crosswind, then turn 225 degrees into the crosswind (teardrop thus reversed). Altitude lost should be the same as (f), but you never know.
j. Like (f) but this time roll into a 45 degree bank while pushing the nose down (at half or zero G as appropriate), ready to pull as soon as the Vbg attitude has been set.
k. Like (f) but use the Mark1234 technique of immediately rolling to 60 degrees bank, pull to the stall warner while the nose drops, play angle of bank against stall once the nose is at the Vbg attitude.
At the end of all items a-k, write down altitude lost.
Further things to note: QNH, OAT, actual weight, actual wind. I will also run an outdoor-type GPS which has track recording so that I can see how big the teardrop shapes are and whether the 225/45 turn without any pause inbetween gets you aligned with the runway centerline. (Any suggestions on how to make sure I'm later able to correlate the GPS track with the test results that I wrote down? Other than making sure my watch is synced with the GPS time, and write down the time of each individual test?)
Any tips on record keeping? Anyone has a handy form or something for this kind of stuff?
Other safety items:
I'll be doing this in the R2160 which is cleared for aerobatics, will be flown within the "A" limits, and I am very current in aeros/spin recovery etc. in this aircraft. I have in the past pulled the mixture to ICO in-flight and I know the engine will windmill above Vs and catch immediately as soon as mixture is restored. Everything will be done at altitude, over an area with plenty emergency landing opportunities. Airspace will be the Rotterdam TMA (class E) with permission/traffic service from ATC.
Any additions?
Please critique my "test plan".
Key numbers from the POH:
Vs = 63 knots (at MTOW)
Vbg = 78 knots (at MTOW) - supposedly yields a 1 in 8.7 glide ratio, and a V/S of ~900 ft/min (to confirm)
Vs in a 45 degree stable descending turn is thus theoretically ~75 knots. Close enough to Vbg to not need to explore the difference in performance between pulling to the stall at 45 degrees, and flying Vbg at 45 degrees. In fact (but to be confirmed) I expect the stall warner to sound continuously, with noticeable buffet, in a 45 degree Vbg stable turn.
Preliminary actions:
HASELL
(i) From height, establish the aircraft in a Vbg stable, trimmed descent. Mark attitude with some sticky tape on the canopy. Write down/time V/S.
(ii) From height, establish the aircraft in a Vbg stable, trimmed descent at 45 degree bank left and right. Mark attitude again with some sticky tape. Write down/time V/S.
(iii) From height, establish the aircraft in a Vbg stable, trimmed descent with the mixture closed. Write down/time V/S.
(i) and (ii) are so that the proper attitude for the subsequent tests can be set quickly. (iii) is to provide data on the difference between throttle closed and mixture closed (prop windmilling), so that all subsequent data points can be corrected for that.
Test items:
All items start from a stable, properly trimmed Vy climb along a line feature, into the wind as far as possible. When passing through a certain safe height (3000' most likely, weather permitting) I'm going to pull the power and:
a. Hold the nose up to see how long it takes for the aircraft to stall. Then recover the stall and see how much time/altitude I lose before in a stable Vbg glide.
b. Hold the stick in the same position, furthermore as in (a).
c. Completely release the stick, let the aircraft sort itself out, furthermore as in (a).
d. Fly the aircraft in a half-G pushover, furthermore as in (a).
e. Fly the aircraft in a ballistic arc (zero G), furthermore as in (a).
(a)-(e) are essentially to see how much "oh ****" time I've got, and how important ingrained reflexes are. If, for instance, (a) delivers the same as (d)/(e) (which I don't expect), the "oh ****" factor isn't all that important.
Subsequent tests include one second of "oh ****" time after closing the throttle, then:
f. Establish Vbg according to the best technique from (a)-(e), then turn into the crosswind 225 degrees at 45 degree bank, turn the other way 45 degrees at 45 degree bank.
g. Same as (e) but with 60 degree bank
h. Same as (e) but with 30 degree bank
(g) and (h) essentially to confirm Rogers
i. Like (f) but start with a left turn 45 degrees away from the crosswind, then turn 225 degrees into the crosswind (teardrop thus reversed). Altitude lost should be the same as (f), but you never know.
j. Like (f) but this time roll into a 45 degree bank while pushing the nose down (at half or zero G as appropriate), ready to pull as soon as the Vbg attitude has been set.
k. Like (f) but use the Mark1234 technique of immediately rolling to 60 degrees bank, pull to the stall warner while the nose drops, play angle of bank against stall once the nose is at the Vbg attitude.
At the end of all items a-k, write down altitude lost.
Further things to note: QNH, OAT, actual weight, actual wind. I will also run an outdoor-type GPS which has track recording so that I can see how big the teardrop shapes are and whether the 225/45 turn without any pause inbetween gets you aligned with the runway centerline. (Any suggestions on how to make sure I'm later able to correlate the GPS track with the test results that I wrote down? Other than making sure my watch is synced with the GPS time, and write down the time of each individual test?)
Any tips on record keeping? Anyone has a handy form or something for this kind of stuff?
Other safety items:
I'll be doing this in the R2160 which is cleared for aerobatics, will be flown within the "A" limits, and I am very current in aeros/spin recovery etc. in this aircraft. I have in the past pulled the mixture to ICO in-flight and I know the engine will windmill above Vs and catch immediately as soon as mixture is restored. Everything will be done at altitude, over an area with plenty emergency landing opportunities. Airspace will be the Rotterdam TMA (class E) with permission/traffic service from ATC.
Any additions?
Last edited by BackPacker; 25th Jan 2012 at 09:48.
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I think the GPS is a good idea, as you never quite know what you will want to analyse later.
Noting the QNH, ground temperature (and ideally the OAT at some relevant height) allows for some CAS/TAS conversions later.
Which is important because at altitude your TAS should be higher and your turn rate (at any given bank angle) should be slower, though the angle of descent should be the same.
Which, if I have this right, means that real turn backs are harder on low density days, with the height loss inversely proportional to density.
Noting the QNH, ground temperature (and ideally the OAT at some relevant height) allows for some CAS/TAS conversions later.
Which is important because at altitude your TAS should be higher and your turn rate (at any given bank angle) should be slower, though the angle of descent should be the same.
Which, if I have this right, means that real turn backs are harder on low density days, with the height loss inversely proportional to density.
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I don't have very high hopes for that GPS. Best it does is one track point per second. And of course the vertical accuracy can be as little as +/- 50 feet. But since I've got that GPS anyway, why not?
A fellow pilot has some professional equipment that's used to accurately track racecars, and he's trying to adapt that for aerobatics tracking. Maybe once that's ready we'll give it another go.
A fellow pilot has some professional equipment that's used to accurately track racecars, and he's trying to adapt that for aerobatics tracking. Maybe once that's ready we'll give it another go.
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The GPS might be more useful than you think. During my PPL training I usually had a Garmin H eTrex in the back. It was much more useful for Nav than analysing circuits though. (I did an awful lot of circuits).
The absolute height accuracy can be well off, eg I tracked my first helicopter solo, and found I picked up and set down at -200ft agl, and no I wasn't in the Netherlands! However the error can be quite stable, which means descent rates can be quite accurate. Headings and turn rates require some assumption about the wind, but can also work out well.
Assuming the unit had enough satellites to start with, the big problem was when it lost or acquired one. That was when you got the sudden jumps. I was pretty sure of the reason because in a circuit the same jumps always occurred when I turned through the same headings.
If you analyse it in a spreadsheet, you can work out the energy change per time step, omit the "impossible" jumps, and look at the trends on either side. So with some effort, even "hiker GPS" data can be useful.
------
Incidentally, in case any PPL students reading this might think GPS tracks are a good way to analyse circuits, my experience suggests not. I never learned anything useful from them. By contrast, GPS tracks were incredibly useful during Nav, not least for showing the FI you had actually gone where you said you did!
The absolute height accuracy can be well off, eg I tracked my first helicopter solo, and found I picked up and set down at -200ft agl, and no I wasn't in the Netherlands! However the error can be quite stable, which means descent rates can be quite accurate. Headings and turn rates require some assumption about the wind, but can also work out well.
Assuming the unit had enough satellites to start with, the big problem was when it lost or acquired one. That was when you got the sudden jumps. I was pretty sure of the reason because in a circuit the same jumps always occurred when I turned through the same headings.
If you analyse it in a spreadsheet, you can work out the energy change per time step, omit the "impossible" jumps, and look at the trends on either side. So with some effort, even "hiker GPS" data can be useful.
------
Incidentally, in case any PPL students reading this might think GPS tracks are a good way to analyse circuits, my experience suggests not. I never learned anything useful from them. By contrast, GPS tracks were incredibly useful during Nav, not least for showing the FI you had actually gone where you said you did!
I got an excellent plot off my GPS from my recent real turnback with a partial loss of power. It helped a lot in my personal debrief.
Backpacker - I do a lot of assessment of flight test plans and flight test reports, but within a structured test environment. I would recommend if you are going to do this safely that you make sure you understand briefing and debriefing for flight test, get somebody else to listen to and critique your brief, understand the use of test cards, and probably fly with an experienced pilot as a safety observer. Also make sure that all of the aspects of flying you'll be demonstrating you are fully current in, before putting them together. The standard technique for assessing difficulty of flying a manoeuvre (usually referred to as "pilot compensation") is the "Cooper Harper Rating Scale" - there's a lot about it on the web, but you may find it useful to run your CH task construction past a test pilot who has done the formal training in its use.
G
Backpacker - I do a lot of assessment of flight test plans and flight test reports, but within a structured test environment. I would recommend if you are going to do this safely that you make sure you understand briefing and debriefing for flight test, get somebody else to listen to and critique your brief, understand the use of test cards, and probably fly with an experienced pilot as a safety observer. Also make sure that all of the aspects of flying you'll be demonstrating you are fully current in, before putting them together. The standard technique for assessing difficulty of flying a manoeuvre (usually referred to as "pilot compensation") is the "Cooper Harper Rating Scale" - there's a lot about it on the web, but you may find it useful to run your CH task construction past a test pilot who has done the formal training in its use.
G
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GPS altitude is normally accurate to within 10-20ft - so long as you get good reception.
However some older products, notably those using the popular SIRF-2 chip, had a systematic altitude error of about 160ft. I can't remember which way it went. Basically they did not correct for the deviation from the ellipsoid, IIRC, which in the UK is a certain fairly constant figure.
However some older products, notably those using the popular SIRF-2 chip, had a systematic altitude error of about 160ft. I can't remember which way it went. Basically they did not correct for the deviation from the ellipsoid, IIRC, which in the UK is a certain fairly constant figure.
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Just a couple of thoughts.
IF you can safely set up a small video (eg a gopro) that can film the panel / altimeter, start it, film the GPS time, then let it run. That way you can sync the two up. Just a variation on the theme of photographing the GPS time so you can geotag photos after the fact. There are also some GPS's (e.g my cycle one) that have baro altitude.)
The other thought is that you don't seem to have a way of considering positioning. I'm not sure it is feasible, but for example e.g. if method 1) makes the turn in 300ft, but leaves you 1/2 a mile further away than method 2), which takes 400ft, which is favoured?
Otherwise, I look forward to the results. In retrospect, I think the my approach probably isn't/wasn't representative, as it pre-supposes you're making the turn.
IF you can safely set up a small video (eg a gopro) that can film the panel / altimeter, start it, film the GPS time, then let it run. That way you can sync the two up. Just a variation on the theme of photographing the GPS time so you can geotag photos after the fact. There are also some GPS's (e.g my cycle one) that have baro altitude.)
The other thought is that you don't seem to have a way of considering positioning. I'm not sure it is feasible, but for example e.g. if method 1) makes the turn in 300ft, but leaves you 1/2 a mile further away than method 2), which takes 400ft, which is favoured?
Otherwise, I look forward to the results. In retrospect, I think the my approach probably isn't/wasn't representative, as it pre-supposes you're making the turn.
GPS altitude is normally accurate to within 10-20ft - so long as you get good reception.
However some older products, notably those using the popular SIRF-2 chip, had a systematic altitude error of about 160ft. I can't remember which way it went. Basically they did not correct for the deviation from the ellipsoid, IIRC, which in the UK is a certain fairly constant figure.
However some older products, notably those using the popular SIRF-2 chip, had a systematic altitude error of about 160ft. I can't remember which way it went. Basically they did not correct for the deviation from the ellipsoid, IIRC, which in the UK is a certain fairly constant figure.
Pretty irrelevant - between start and end of the manoeuvre, the total altitude change will be below 1000ft in probably any light aeroplane. In analysing something like this, it's just differences, not absolute values - and the GPS is in that case, giving a more exact reading than anything a pressure altimeter will give you anyhow since it's unaffected by PEC.
OAT and pressure altitude will give density altitude near enough, and those can just be recorded at stable conditions before manouevring.
Even if flying take-off to landing for a manoeuvre like this, the same applies for data analysis because GPS will flatline on the runway (and given that PEC varies with airspeed and may be affected by ground effect, a pressure altimeter may not, although it'll be close enough to allow analysis if you had airspeed as well).
G