Full flap landing rquired

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rookiepilot
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Re: Full flap landing rquired

Post by rookiepilot » Sat Jun 29, 2019 1:19 pm

GoinVertical wrote:
Sat Jun 29, 2019 7:04 am
When I was instructing, we used to teach students to maintain 3 white, 1 red on the PAPIs. Keeps you a bit steeper than 3 degrees while allowing them to still show deviation.
That's how I'd do it, transitioning to 2 and 2 short final, and even closer to three red one white over the threshold, to land 500 past the numbers
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Re: Full flap landing rquired

Post by photofly » Sat Jun 29, 2019 2:24 pm

digits_ wrote:
Sat Jun 29, 2019 12:28 pm
You are not flying the whole approach at 60 kts. Only the last part. If you calculate it with an average 75 kts (80kts downwind-base, 70 base-final), which seems to be the speed FTUs around here use for a 172, you end up with a 75*5.5 = 413 ftpm.
If your g/s average is 70 during the descent you're flying a 172 too fast. And an 8nm circuit is positively ginormous.

Philosophically I just don't believe a constant approach slope makes any sense in a tiny aircraft that flies very slowly. Another reason: There will be big power variations day-to-day because of different wind conditions. My preference is to keep the circuit tighter when the winds are stronger. If you're trying to follow fixed visual guidance from the ground then you have huge power variations from one day to the next, instead.
A big part of students will end up commercially at some point, getting used to a 3 degree glide slope right away is pretty valuable.
I suppose that depends on what your student body is like. On the national average, only a very small proportion of pilots go further than a PPL, and only a proportion of those fly a transport aircraft. Getting used to a a 3° approach is actually worse than useless for most pilots because it's not the right approach for any aircraft they will ever fly; it's certainly not the right approach for the aircraft they're using for ab-initio training.

I'm not sure that following a PAPI does actually teach you what a 3° slope looks like; if it was possible to learn what a 3° slope looked like with any reliability, there would be no need for a PAPI outside of a training environment, because every pilot would already know what the right slope looked like; we wouldn't need visual assistance.

Given the number of runways that PPLs do - and will - use that don't have slope guidance I believe its better training to learn to land entirely visually, and ignore the PAPI or VASI, if there should be one. For night flying, Instrument training, or later in training as an "oddity" I can see the point of introducing visual slope guidance.
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Re: Full flap landing rquired

Post by 5x5 » Sat Jun 29, 2019 2:54 pm

photofly wrote:
Sat Jun 29, 2019 2:24 pm

Given the number of runways that PPLs do - and will - use that don't have slope guidance I believe its better training to learn to land entirely visually, and ignore the PAPI or VASI, if there should be one.
Absolutely this!! The only value for PAPIs is as I said before to be a last chance warning you're too low. And what do you do if that should occur anywhere else than very short final - overshoot! The night flights we're discussing are VFR and the procedures you need to teach or learn are visual ones. Trying to introduce a half-baked IFR concept and procedure into a situation that is already more risky than flight in the day is mind-boggling to me.
digits_ wrote:
Fri Jun 28, 2019 8:29 am
Why would you *not* fly a papi at night? Especially when learning to fly approaches at night, it is a valuable tool to get used to what a 3 degree glideslope looks like at night. Being too high is as big of a challenge as being too low when learning to fly at night, albeit with less severe consequences when you get it wrong.
You already got it partly right that being high can be a challenge at night, but rather than having less severe consequences there are virtually no consequences since if you're high you simply overshoot and set-up better and correctly the next time.

Trying to fly a 3°glidepath and doing it poorly could very easily kill you. And I'd bet quite a bit of money that anyone being trained for a night rating (quite inexperienced pilot generally) who is trying to follow the PAPIs and fly a shallow glidepath will be doing it poorly/unsafely.
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Re: Full flap landing rquired

Post by digits_ » Sat Jun 29, 2019 3:01 pm

photofly wrote:
Sat Jun 29, 2019 2:24 pm
If your g/s average is 70 during the descent you're flying a 172 too fast.
Why? Not sure what the issue is here. Below 85 kts you can put the first flaps dow, so fly 75 kts at the first part, and then the final approach speed for the last 300 ft. You'll average out on about 70 I'd estimate.
photofly wrote:
Sat Jun 29, 2019 2:24 pm
And an 8nm circuit is positively ginormous.
If you measure it out in google earth, what circuit length do you end up with? The 8 nm is what I end up with on a 7000 ft runway if I overlay the circuit. It was certainly bigger than I expected.
photofly wrote:
Sat Jun 29, 2019 2:24 pm
Philosophically I just don't believe a constant approach slope makes any sense in a tiny aircraft that flies very slowly. Another reason: There will be big power variations day-to-day because of different wind conditions. My preference is to keep the circuit tighter when the winds are stronger. If you're trying to follow fixed visual guidance from the ground then you have huge power variations from one day to the next, instead.
Isn't that a part of students getting used to the effect of wind? If you want to keep the power constant, you'll end up with glideslope differences from one day to the next. For people learning to land, I'd say a different glideslope angle every day is worse than a different power setting.
A big part of students will end up commercially at some point, getting used to a 3 degree glide slope right away is pretty valuable.
I suppose that depends on what your student body is like. On the national average, only a very small proportion of pilots go further than a PPL, and only a proportion of those fly a transport aircraft.
That's true.
photofly wrote:
Sat Jun 29, 2019 2:24 pm
Getting used to a a 3° approach is actually worse than useless for most pilots because it's not the right approach for any aircraft they will ever fly; it's certainly not the right approach for the aircraft they're using for ab-initio training.
I agree it is not necessary for a 172 to fly at a 3 degree glideslope, but I don't see anything wrong with it either. You have to teach them something in the beginning, as they have never landed a plane before.
photofly wrote:
Sat Jun 29, 2019 2:24 pm

I'm not sure that following a PAPI does actually teach you what a 3° slope looks like; if it was possible to learn what a 3° slope looked like with any reliability, there would be no need for a PAPI outside of a training environment, because every pilot would already know what the right slope looked like; we wouldn't need visual assistance.
Of course you can learn what a 3 degree slope looks like. PAPIs aren't required per se during the day, but it makes life a bit easier. Just like you don't need centerline to land in the middle of a runway, or centerline lights at night, but boy does it make life easier.

Regardless of the exact degree of glideslope that you use, I assume you teach students to recognize when they are too high or too low for certain points in the approach. If they can recognize that, why wouldn't they be able to recognize a 3 degree-ish glideslope?
photofly wrote:
Sat Jun 29, 2019 2:24 pm

Given the number of runways that PPLs do - and will - use that don't have slope guidance I believe its better training to learn to land entirely visually, and ignore the PAPI or VASI, if there should be one. For night flying, Instrument training, or later in training as an "oddity" I can see the point of introducing visual slope guidance.
Pilots have to be able to land on a runway without slope guidance, no argument there. But if you do happen to end up on a runway with a PAPI, I don't see why you should ignore it, or why an instructor gets questioned for teaching a student to use the PAPI at night. If anything, I would consider teaching pilots not to use a PAPI at night bad airmanship.
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Re: Full flap landing rquired

Post by digits_ » Sat Jun 29, 2019 3:05 pm

5x5 wrote:
Sat Jun 29, 2019 2:54 pm

Trying to fly a 3°glidepath and doing it poorly could very easily kill you. And I'd bet quite a bit of money that anyone being trained for a night rating (quite inexperienced pilot generally) who is trying to follow the PAPIs and fly a shallow glidepath will be doing it poorly/unsafely.
Why? How? I really don't get it.

Flying a steady 400 fpm descent with papis at night is less safe than a 600 - 800 fpm descent without any guidance?

How?
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Re: Full flap landing rquired

Post by photofly » Sat Jun 29, 2019 3:50 pm

digits_ wrote:
Sat Jun 29, 2019 3:01 pm

If you measure it out in google earth, what circuit length do you end up with?
5nm. Shorter when instructed to "keep it in tight".
digits_ wrote:
Sat Jun 29, 2019 3:01 pm
Isn't that a part of students getting used to the effect of wind? If you want to keep the power constant, you'll end up with glideslope differences from one day to the next. For people learning to land, I'd say a different glideslope angle every day is worse than a different power setting.
I'd rather students selected a consistent configuration, power setting and timing for flaps, to give a consistent rate of descent. For me, getting used to the effects of the wind is deciding when to turn base, and when to begin the descent.

I don't really care about descent angle, because (unless you're trying to follow a PAPI) it's not likely to remain constant, important, or easily measured. Since I don't care about the PAPI it's not worth worrying about. What I care about is correct airspeed, and "are we going to make it to the runway?".
digits_ wrote:
Sat Jun 29, 2019 3:01 pm
Regardless of the exact degree of glideslope that you use, I assume you teach students to recognize when they are too high or too low for certain points in the approach. If they can recognize that, why wouldn't they be able to recognize a 3 degree-ish glideslope?
It's important to recognize whether the touchdown zone is moving up towards the horizon (undershooting) or moving away from the horizon. As long as the touchdown zone maintains a steady angle from the horizon and the airspeed is correct, I'm not fussed for what that angle is.

By the way, John Denker has a cute way to judge your approach angle: the first knuckle of your thumb at arm's length subtends about 4°. I often check with that, when lined up with the runway, but only for kicks.
https://www.av8n.com/how/htm/landing.html#sec-thumb

Absolutely you can land a 172 at 3°, and if one gets too low early in an approach, that's what you end up doing: no harm, no foul. It's just not my target for an "average" approach.
But if you do happen to end up on a runway with a PAPI, I don't see why you should ignore it, or why an instructor gets questioned for teaching a student to use the PAPI at night. If anything, I would consider teaching pilots not to use a PAPI at night bad airmanship.
During the day I ignore it because it's guiding me towards something I don't want to do. At night, I recognize the extra danger caused by the difficulty of judging a long straight-in approach in the dark and I would alway reference a PAPI if there is one. That means my night approaches are different to my day ones; so be it.
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Re: Full flap landing rquired

Post by digits_ » Sat Jun 29, 2019 4:17 pm

photofly wrote:
Sat Jun 29, 2019 3:50 pm
digits_ wrote:
Sat Jun 29, 2019 3:01 pm

If you measure it out in google earth, what circuit length do you end up with?
5nm. Shorter when instructed to "keep it in tight".
For what runway length?
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Re: Full flap landing rquired

Post by photofly » Sat Jun 29, 2019 6:03 pm

I just measured it out on Google maps. A tight-ish circuit is 4.3nm, including the 4000' runway. Track distance (not including the runway) is 3.7nm.
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Re: Full flap landing rquired

Post by digits_ » Sat Jun 29, 2019 7:06 pm

photofly wrote:
Sat Jun 29, 2019 3:50 pm
digits_ wrote:
Sat Jun 29, 2019 3:01 pm

If you measure it out in google earth, what circuit length do you end up with?
5nm. Shorter when instructed to "keep it in tight".
digits_ wrote:
Sat Jun 29, 2019 3:01 pm
Isn't that a part of students getting used to the effect of wind? If you want to keep the power constant, you'll end up with glideslope differences from one day to the next. For people learning to land, I'd say a different glideslope angle every day is worse than a different power setting.
I'd rather students selected a consistent configuration, power setting and timing for flaps, to give a consistent rate of descent. For me, getting used to the effects of the wind is deciding when to turn base, and when to begin the descent.
How does that technique hold up in a controlled field where tower tells them when to turn base? Lot's of people learn to fly in controlled airspace where they don't have the luxury to turn based on the wind.

If you teach them to end up on a fixed approach path (3 degree ish in my example, but you could pick whatever value as long as you stick with it), then it doesn't matter what happens before the short final, as soon as they end up on their pre-practiced slope for the last half mile/mile/... everything will be fine.
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Re: Full flap landing rquired

Post by photofly » Sat Jun 29, 2019 7:22 pm

digits_ wrote:
Sat Jun 29, 2019 7:06 pm

How does that technique hold up in a controlled field where tower tells them when to turn base? Lot's of people learn to fly in controlled airspace where they don't have the luxury to turn based on the wind.

If you teach them to end up on a fixed approach path (3 degree ish in my example, but you could pick whatever value as long as you stick with it), then it doesn't matter what happens before the short final, as soon as they end up on their pre-practiced slope for the last half mile/mile/... everything will be fine.
It is at a controlled field, and the Tower controller frequently instructs aircraft when to turn base, or extend the downwind. If required to extend; just stay at circuit altitude until you're ready to descend. If told to turn in early, use less power. Make it a power-off approach, if that will work. Or add flaps early, and slip if necessary. You can make a 7 or 8° or 10° approach. That's the flexibility of flying a small plane that perhaps you don't have in a transport aircraft. Which is why approach constraints (like a 3°glideslope) aren't appropriate for something like a 172, for me.
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Re: Full flap landing rquired

Post by C.W.E. » Sat Jun 29, 2019 9:38 pm

Teaching the same approach profile over and over results in having trained a robot.
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Re: Full flap landing rquired

Post by rotorspeed » Sun Jun 30, 2019 10:05 pm

I have no problem judging the descent to the runway without the PAPI. I've never flown one at any of the airports in the years I've been flying in BC until recently, I'm guessing a year, that Pitt got a PAPI. I find flying the PAPI is good training to fly more precise staying on the glideslope it takes a bit more precision in regards to keeping a constant approach
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Re: Full flap landing rquired

Post by Guill » Mon Aug 05, 2019 12:48 am

photofly wrote:
Sat Jun 29, 2019 11:34 am
digits_ wrote:
Sat Jun 29, 2019 6:22 am

So what is a natural or reasonable descent rate in a small aircraft? How many degrees glideslope should one use?
500fpm, at 60 kts g/s is 5°. Steeper if you like power-off approaches.
If you fly a 3° approach in a circuit from 1000 agl you're flying more than three track miles from the point when you start your descent, which is quite absurd: it's a space-shuttle sized circuit and will thoroughly piss off everyone else in the same air as you.
digits_ wrote:
Sat Jun 29, 2019 6:22 am
What about IFR approaches in small aircraft?
IFR approaches are all designed for transport aircraft, but a Cessna 172 is not a Boeing 737. Of course you can emulate their approach path, if you have to, but it's a terrible way to fly in VFR conditions.
what if we extend to full flaps later? Somewhere around a quarter mile from threshold? Just be stabilised before 200 agl
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