Threadjack from ILS approaches

spiderweb

spiderweb

Final Approach
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Ben
"Gear down, flaps down one notch, reduce power and pitch for 500 fpm descent." I'm not even going to tell you my approach, because it will get jumped on. But seriously, in an incredibly bumpy ride, or even one with "swells" where you can't get the VSI to settle, what do YOU do?

OK, fine! I'll tell you what I do. I close my eyes, and push a little on the yoke with my forehead. I sing "Happy Birthday to you" 1.5 times, put in a bit of right rudder, and eat half a jelly donut. When I look at the needles, they seem pretty good or whatever. . . .

(Bet you can't jump on THAT technique!)
 
spiderweb said:
"Gear down, flaps down one notch, reduce power and pitch for 500 fpm descent." I'm not even going to tell you my approach, because it will get jumped on. But seriously, in an incredibly bumpy ride, or even one with "swells" where you can't get the VSI to settle, what do YOU do?

OK, fine! I'll tell you what I do. I close my eyes, and push a little on the yoke with my forehead. I sing "Happy Birthday to you" 1.5 times, put in a bit of right rudder, and eat half a jelly donut. When I look at the needles, they seem pretty good or whatever. . . .

(Bet you can't jump on THAT technique!)
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Does this apply to LPV approaches too?

If so, I'm going to try it with my instructor on Friday.
 
spiderweb said:
"Gear down, flaps down one notch, reduce power and pitch for 500 fpm descent." I'm not even going to tell you my approach, because it will get jumped on. But seriously, in an incredibly bumpy ride, or even one with "swells" where you can't get the VSI to settle, what do YOU do?
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Hold pitch and power for what I think is the desired descent gradient, get a trend from the GS needles average position, and adjust pitch and power accordingly. And in turbulence, I wouldn't much care what the VSI said -- there are good reasons the FAA doesn't even require a VSI for IFR flight.
 
Oh brother.... :rolleyes2:

Set descent rate with known pitch/power, scan to maintain localizer (AI, DG), high on GS is ok, low is not.
 
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when it's really bumpy, I concentrate on keeping the localizer centered and the GS needle centered to one dot low. Generally if it's bumpy the air is active enough that the ceilings aren't going to be THAT low, and if I'm a bit high that will still work out ok. I try not to panic about temporary excursions unless I go BELOW the GS - that gets immediate reaction.

<sarcasm> Oh, and when I get really sick of it, I just pause the sim and take a break. </sarcasm>
 
I fly the approach inverted, just to make it more challenging. :D
 
COFlyBoy said:
Oooh cool. I guess you have to remember to fly opposite of the glideslope needle, like on a back course approach.
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Exactly. And don't forget to kill one of your engines.

Note: I only do this in flight sim.
 
spiderweb said:
"Gear down, flaps down one notch, reduce power and pitch for 500 fpm descent." I'm not even going to tell you my approach, because it will get jumped on. But seriously, in an incredibly bumpy ride, or even one with "swells" where you can't get the VSI to settle, what do YOU do?
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Turn on the autopilot. :D

Actually, one of the first things I do when getting checked out in a new plane these days is to determine the IFR configurations - Pitch, power setting, airspeed, and vertical speed for initial climb, cruise climb, cruise, cruise descent, approach level, precision approach descent, and non-precision approach descent.

So, in the above situation, I would set the power to the predetermined level, maintain pitch as much as possible, and it should average out fairly evenly going through the bumps.

OK, fine! I'll tell you what I do. I close my eyes, and push a little on the yoke with my forehead. I sing "Happy Birthday to you" 1.5 times, put in a bit of right rudder, and eat half a jelly donut. When I look at the needles, they seem pretty good or whatever. . . .
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:rofl:
 
TMetzinger said:
when it's really bumpy, I concentrate on keeping the localizer centered and the GS needle centered to one dot low. Generally if it's bumpy the air is active enough that the ceilings aren't going to be THAT low, and if I'm a bit high that will still work out ok. I try not to panic about temporary excursions unless I go BELOW the GS - that gets immediate reaction.
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I fly and teach aiming to keep the GS needle centered. If you aim high, you reduce your margin for error before you reach the limit. Thus, I don't react any faster or with more "panic" for deviations in either direction. As long as it stays close to the center, I'm pretty good with it no matter which way it's off, but as it approaches 1/2 scale, I get a lot more aggressive, but equally so for either up or down.
 
try to keep the needles more or less centered
 
Ron Levy said:
I fly and teach aiming to keep the GS needle centered. If you aim high, you reduce your margin for error before you reach the limit. Thus, I don't react any faster or with more "panic" for deviations in either direction. As long as it stays close to the center, I'm pretty good with it no matter which way it's off, but as it approaches 1/2 scale, I get a lot more aggressive, but equally so for either up or down.
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Stuff that can kill me = below the glideslope
Lots of air = above the glideslope

We're flying small airplanes -- if we're a dot high more flaps or even a slip can easily bleed off the excess altitude.
 
dmccormack said:
Stuff that can kill me = below the glideslope
Lots of air = above the glideslope

We're flying small airplanes -- if we're a dot high more flaps or even a slip can easily bleed off the excess altitude.
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That's true, but why not aim for centered needles, plain and simple? Even going from a C172 or Archer up to a Saratoga, it really pays to be right on the money.
 
spiderweb said:
That's true, but why not aim for centered needles, plain and simple?
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Whether it comes to altitude, or GS, or spot landings, I've always been a believer in the Sundance Kid's advice to Butch Cassidy about shooting someone -- "Aim for the middle. That way, if you miss, you still hit something." When talking about GS, if you aim for the middle and keep it within tolerances, you won't hit anything hard, and you make it twice as easy compared to limiting yourself to only the top half of the tolerance box. Yeah, we always strive for perfection, but since perfection is centered, why not aim for it to start with?
 
dmccormack said:
Of course!!

But I'll take a bit high on GS over low if that's the current set of options.

:D
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Me too, but as my CFII reminded me, as far as the PTS is concerned, full scale high is just as much a bust as full scale low.
 
azure said:
Me too, but as my CFII reminded me, as far as the PTS is concerned, full scale high is just as much a bust as full scale low.
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While I agree, a full scale high has a much better safety factor than a full scale low.

It is worth noting that there are times when flying a dot or two low on approach can have a purpose. Such as you're flying into a Bravo airport in a Mooney and told "Keep your speed up for 737 traffic behind you." Having a slippery airplane and going down the pike quickly means you need to slow it down somehow.
 
Sure, but as far as I'm concerned, a dot or two is cause for making an immediately correction before it gets to half scale... then 3/4... then full scale. Especially in the last 500 feet.

And Ted, that's exactly the technique my CFII recommended when we were doing full-bore ILS's last year at some of our local controlled fields in a 172. Not the slipperiest bird, but it's mighty busy and they won't be happy if you slow down into the white arc much before DA. When you're ready to add that first notch of flaps, if you're a tad low you won't balloon full-scale high.

That said, I don't think a DPE would be too happy with a candidate intentionally going below GS for any reason. So I'm glad I'll be doing my checkride in the Cardinal... I just wish this rash of mx problems would end. :sad:
 
dmccormack said:
Full scale <> acceptable

I was talking about a dot or two.
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For the IR ride, half-scale is the limit, and that's the first mark vertically on some CDI's, so make sure you know how many dots you have to play with. Also, if you aim to keep it "a dot or two" on the high side, you're toying with a bust on the ride because your error margin is now only a quarter-scale or less instead of half-scale. Aim for the middle, and you've got the entire middle half to play with. Finally, keep in mind that all the false glide path signals are on the high side (none permitted on the low side, and that's one reason you see all the warnings about not intercepting from above).
 
Ron Levy said:
For the IR ride, half-scale is the limit, and that's the first mark vertically on some CDI's, so make sure you know how many dots you have to play with. Also, if you aim to keep it "a dot or two" on the high side, you're toying with a bust on the ride because your error margin is now only a quarter-scale or less instead of half-scale. Aim for the middle, and you've got the entire middle half to play with. Finally, keep in mind that all the false glide path signals are on the high side (none permitted on the low side, and that's one reason you see all the warnings about not intercepting from above).
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Actual IFR ops <> IR Test prep
 
azure said:
Sure, but as far as I'm concerned, a dot or two is cause for making an immediately correction before it gets to half scale... then 3/4... then full scale. Especially in the last 500 feet.

And Ted, that's exactly the technique my CFII recommended when we were doing full-bore ILS's last year at some of our local controlled fields in a 172. Not the slipperiest bird, but it's mighty busy and they won't be happy if you slow down into the white arc much before DA. When you're ready to add that first notch of flaps, if you're a tad low you won't balloon full-scale high.

That said, I don't think a DPE would be too happy with a candidate intentionally going below GS for any reason. So I'm glad I'll be doing my checkride in the Cardinal... I just wish this rash of mx problems would end. :sad:
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dmccormack said:
Actual IFR ops <> IR Test prep
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Exactly...

Shoot a couple of real ILSs at 190 over the ground and that becomes clear.
 
Ted DuPuis said:
It is worth noting that there are times when flying a dot or two low on approach can have a purpose. Such as you're flying into a Bravo airport in a Mooney and told "Keep your speed up for 737 traffic behind you." Having a slippery airplane and going down the pike quickly means you need to slow it down somehow.
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Exactly - If I'm going into a busy airport and I'm in VMC, I will often let myself get low knowing that when I approach the fence I'll be pulling power and pitching up to slow down/drop the flaps and gear.

The caveat is that I won't do that while in IMC or if I'm following a jet close behind.
 
Fearless Tower said:
Exactly - If I'm going into a busy airport and I'm in VMC, I will often let myself get low knowing that when I approach the fence I'll be pulling power and pitching up to slow down/drop the flaps and gear.

The caveat is that I won't do that while in IMC or if I'm following a jet close behind.
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I agree with this. And in the early part of an approach I'm fine with slop on both sides of the center. But when I'm getting closer to the earth, a deviation hi means I might have to miss the approach. A deviation low means I might die. Guess which gets the more immediate response if workload is high?
 
We all seem to be in pretty violent agreement here. As I said, "especially in the last 500 feet", I'm going to correct immediately if I get even a dot off. Not so critical at 2000 AGL or just past the published GS intercept, but if I'm prepping for the checkride (as I am now) or going for an IPC (which I will be someday), the PTS rules and I don't want to waste my margin against a bust if I can help it.

And yes, I typically aim for the high side of the VGSI when visual (3 whites if it's got 4) and generally believe that a little high is better than a little low (unless I'm about to increase my AOA drastically to slow down). But when I'm flying to satisfy the examiner, it's right down the middle as best I can.
 
Maybe it's my Navy carrier experience, where "high" could mean a bolter (the target wire being #3 of 4) but "low" could still mean a trap on one of the first two wires, but I'm still a firm believer in aiming for centered needle (and 2 red/2 white on PAPI's), if nothing else as a matter of pride and aiming for that elusive perfection. YMMV.
 
TMetzinger said:
I agree with this. And in the early part of an approach I'm fine with slop on both sides of the center. But when I'm getting closer to the earth, a deviation hi means I might have to miss the approach. A deviation low means I might die. Guess which gets the more immediate response if workload is high?
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I hear this a lot but IMO the reality is often that once inside the FAF you may have less room below you a short way down the GS than you have further on due to obstructions that poke up towards the GS center. Out here in the flatlands it's common to find entirely flat terrain under the GS with nothing taller than the proverbial FAA approved 50 ft tree but it's also not uncommon to have tall buildings and towers situated such that there's much less clearance than you might expect when you're 1200 ft above the runway. Having a mental image of a Kansas prairie below the ILS might be comforting but that comfort could easily be an illusion.

And while it's true that you can always go missed if you end up a few dots high, there's a big temptation to "fix" an approach from 3 dots high by ramping up the descent rate and that has undoubtedly led to more than a few CFIT accidents.

For those reasons I tend to give equal priority to high and low indications and consider the risk of being low to be relatively constant during the descent past the FAF.
 
Ron Levy said:
Maybe it's my Navy carrier experience, where "high" could mean a bolter (the target wire being #3 of 4) but "low" could still mean a trap on one of the first two wires, but I'm still a firm believer in aiming for centered needle (and 2 red/2 white on PAPI's), if nothing else as a matter of pride and aiming for that elusive perfection. YMMV.
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No argument - I don't "aim" to be high - I want centered needles. I just place more weight on fixin below the glideslope than above it, when there are multiple things to correct.

Example. I'm 1 dot low and 2 dots right - still within half scale (my CDI has six dots for full scale) but I'm sure to fix being low while attempting to fix being right - low is more important.
I'm 1 dot high and 2 dots left - I want to fix both but being left might be more important than being high at that point on the approach.
 
One thing about the idea of not worrying to much about centering until you get closer in: I know it is easier to center while still far out, so I try to lock in then, because keeping something centered is easier than trying to get rid of slop near the end.
 
spiderweb said:
One thing about the idea of not worrying to much about centering until you get closer in: I know it is easier to center while still far out, so I try to lock in then, because keeping something centered is easier than trying to get rid of slop near the end.
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True - but remember that the intial discussion of "slop" was due to turbulence, not laziness.
 
TMetzinger said:
True - but remember that the intial discussion of "slop" was due to turbulence, not laziness.
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Right, good point!

I wonder if anyone, in mild turbulence, let's the AP intercept the needles, set proper power and gear/flaps as indicated. Let George get it stable with the correct configuration, then take over. Usually I just fly the whole thing.
 
spiderweb said:
Right, good point!

I wonder if anyone, in mild turbulence, let's the AP intercept the needles, set proper power and gear/flaps as indicated. Let George get it stable with the correct configuration, then take over. Usually I just fly the whole thing.
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If anything, I do it the other way around - hand fly the intercept and stabilize before turning it over to the A/P. In reality, most of the time, I just keep it in manual all the way to the ground. I tend to hit the A/P disconnect after completing the final vector to intercept if I am using autopilot at all. Sadly, in most of the club planes I fly, I just don't trust the autopilots.
 
spiderweb said:
I wonder if anyone, in mild turbulence, let's the AP intercept the needles, set proper power and gear/flaps as indicated. Let George get it stable with the correct configuration, then take over. Usually I just fly the whole thing.
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Turbulence or not, I think this really depends on the autopilot. Some are much better at intercepting a course than others.
 
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gismo said:
I hear this a lot but IMO the reality is often that once inside the FAF you may have less room below you a short way down the GS than you have further on due to obstructions that poke up towards the GS center. Out here in the flatlands it's common to find entirely flat terrain under the GS with nothing taller than the proverbial FAA approved 50 ft tree but it's also not uncommon to have tall buildings and towers situated such that there's much less clearance than you might expect when you're 1200 ft above the runway. Having a mental image of a Kansas prairie below the ILS might be comforting but that comfort could easily be an illusion.
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That's a good point I wasn't thinking about (as I don't fly them for real yet) and I really need to go look it up to remind myself of just how much obstacle protection an ILS GS gives you. But the difference between one dot and full scale represents a much greater absolute vertical distance at 2000 AGL than it does at 500 AGL, which is why I'm more concerned with one dot low close to the ground as opposed to back near the FAF.
 
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spiderweb said:
I wonder if anyone, in mild turbulence, let's the AP intercept the needles, set proper power and gear/flaps as indicated. Let George get it stable with the correct configuration, then take over. Usually I just fly the whole thing.
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I sometimes do that when leveling off in mild turbulence, especially if I'm looking for charts or something (and I've a pax to look out for traffic), and it does a good job. I've never tried my AP on an ILS (it's a STEC-20 now, so no internal pitch control -- I don't think it can capture an ILS GS), but there's no other way to arm the external PSS unit (that I know of) to capture a LPV or LNAV+V GS except from below. So it's either use it to get stabilized then disengage, or ride it all the way down, or hand fly the whole thing. The last time I tried it, it was rock steady so I'd not have qualms about using it for real, but since I'm just training, I pretty much hand fly it except when I need to show my CFII that I still know how to use it.
 
Ron Levy said:
Maybe it's my Navy carrier experience, where "high" could mean a bolter (the target wire being #3 of 4) but "low" could still mean a trap on one of the first two wires,
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For the pilot of the Navy plane, yes. As for the NFO (you) you're pretty much just along for the ride.
 
TMetzinger said:
No argument - I don't "aim" to be high - I want centered needles. I just place more weight on fixin below the glideslope than above it, when there are multiple things to correct.
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For the reasons Lance mentioned (among others), I'm equally concerned by high or low, especially in close.
 
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