The Great Ongoing Aviation Thread (general and other)

The ideal is to fly idle from top of descent to about 800 AGL if VMC. Then throttle up. Anything else is wasting fuel. We rarely achieve the complete ideal. But rather often unless traffic is tick or conditions are nasty, we can cruie at e.g. 10,000 feet in the outer traffic pattern then go to idle for all the subsequent descent and slowing until we add power on short-ish final at 800 AGL to be all squared away by 500 AGL.

I can also imagine somebody vectored to get to the FAF altitude early, and having to drag in from there at ~half flaps and maybe gear. At the FAF they need to re-commence descent and slow, by pulling the power to idle, adding the last couple of notches of flaps as they slow the last 20-40 knots, then re-add power again as the speed decays to the target value, ideally again at about 800 AGL.

Some of the engines howl a lot during engine deceleration = spool-down as the excess bleed air is dumped off the compressor. Maybe the OP is hearing them doing that at / near the FAF.

ATC has a nasty habit of wanting us to maintain speeds that are convenient for them, not us. And often leaves us wishing for better smoothness to be able to hang another notch of flaps or to slow more gradually. But instead we need to use major throttle excursions, sudden slowing, and late-but-not-too-late final configuration to squeeze 3 extra planes per hour into a given runway.

All part of being part of a highly optimized traffic-compressed high-throughput system.

The airport pattern may have changed, minor repairs on a section of runway moved the ideal touchdown point, as LSL mentioned - a major airline customer may have changed/added a certain type of jet with different tenor, a new noise abatement policy, or wax fell out of the OP ear. Not a jab, my hearing comes and goes with changes in pressure or internal stuffiness. I’ll pop from negative pressure in my inner ear to normal just blowing my nose.

That’s probably it, the sound of the compressor dumping. I looked up the A320 and a lot of the carriers operating here have them in their fleet (according to wiki). I’ll correct myself and reassign that sound when I hear it.

And I’ll completely speculate that there was a model or design change in the last few years that makes the sound more common here now. And while I was typing that sentence, I recalled a memory of some trouble with Boeing a few years ago; maybe some carriers switched equipment entirely. And while typing both of those, I missed smithsb’s thoughtful response (no jab taken, btw).

I would add with relative confidence that the planes operated by Southwest Airlines don’t make this sound.

Do you hear it in the Airbus’ cockpit? Have any of you folk heard the sound I’m describing?

Some wrap-up comments (not meaning to end the topic, just batting cleanup on loose ends) …

Southwest operates the 737 exclusively. Many other carriers, including mine, use them too albeit not exclusively. And no, 737s do not make the distinctive penetrating howl, although they do make a distinct sound during throttle-back for the same reason.

Unlike the 737, the A320 series is available with a variety of engines makes & models. I forget which engine model it is that is especially howly. It might be interesting for @oligArchie to try to ID the airline(s) that’re making all the new noise.

Ballpark descent angles on final approach amount to ~300 feet per mile, so if you’re exactly 5 miles from the runway end you’d expect most airplanes (large or small, fast or slow) to be at about 1500 feet above the airport. Which may be more or less versus your house’s altitude if you’re in hilly country.

The actual speedbrakes / spoilers are generally not deployed during the latter stages of approach. Flaps create sufficient drag and in many (not all) aircraft types spoiler-type speedbrakes are prohibited beyond a certain amount of flap deflection; just too much weirdness going on out on the wing if you use both.

Returning to a point @Magiver made that I glossed over. …
He’s right that in a jet, flying the last bit of an approach and landing at idle would be actively dangerous. Don’t do that.

Which is why the general rule is to be fully settled down and with power stabilized well above idle by 500 feet, or about 40 seconds before touchdown. That’s in good weather. In cloudy weather the usual rule is to be settled down (“stabilized approach” in the argot) by 1000 feet ~= 70-80 seconds to touchdown. In truly crap weather, be that gusty sheary driving rain showers or snowy glop it’s further backed out to around 1500 feet = 2 minutes to touchdown.

Well it’s hard to relate a noise heard on the ground to what we hear in the cockpit. I can hear the PW1000G engine on our A320neos doing a bad impression of a whale when spooling up on the ground but I don’t hear it airborne. On the other hand I can hear the speed-brake noise quite clearly in the air.

The A320neo entered service in 2016 so if it’s engine noise you’re hearing that would tie in.

Indeed. The arrival and departure procedures were updated at my home airport within the last 12 months without much, if any, consultation with the airlines. The result is an arrival procedure that the A320 doesn’t think it can fly due to some unrealistic height restrictions. It can actually fly it but only if the pilots use drag, ie speed-brakes, to help with the descent. Our preference is to go direct to a waypoint that skips most of the height restrictions and ATC are normally obliging. The result is that we are either using speed-brakes where we didn’t used to or we are flying a slightly different route. This would change the sound profile for people living near by.

The A320 howl dates from long before the NEO came out. Where I lived from 2001 to 2013 one of the regular arrival tracks came nearly over my house at ~4000 AGL. You always knew when you heard that noise that some A320 was idling in.

It’s quite a distinctive noise. Since it sounds nothing like the CFM56 powered 737 I’m going to bet it’s the IAE V2500 powered variant of teh A320 rather than the ones with CFM56s.

Yeah must be. I’ve never been lucky enough to live under a flight path so I’m not even sure what the noise sounds like.

Lucky you. Every single jet coming into LAX from points east flies directly over my house. Granted, it’s at 10,000ft., but directly over. I sit on the patio in the evening and watch them go over, trying to spot them before the sound alerts me.

I got to thinking about the reduced power approach. That would, by design, steepen the angle of descent which I would expect to increase wingtip vortices and make it harder for the trailing planes.

Not really. Rather than idle thrust creating a steeper approach it is allowing the aircraft to fly a standard approach angle while slowing down. Even then the standard 3° approach is pretty close to a jet’s glide anyway and even with thrust at idle you’re having to drop flap and gear to slow down.

Interesting. I’ve never had anything beyond flaps in a little airplane and reducing power was an elevator ride down.

on a completely different note, is there any thought to ditching in water by dropping a wing first in an attempt to spin it like a ground loop. That Oshkosh fatal T6 crash in the lake almost certainly flipped over. They had trouble retrieving the pilot’s body which I took to mean the plane settled upside down.

I don’t see any way of stopping a conventional water ditching without flipping. In a high wing you end up above the wing with a chance to get out. A low wing is just going to be ugly trying to escape.

I had a flight instructor once who said that I should fly the approach such that if the engine failed, I could still make it to the runway. The question I had, but never quite articulated at the time, was about what happens if the engine doesn’t fail. If I have enough height to glide to the touchdown point, then any extra thrust from a running engine is going to carry me past the desired touchdown point.

That was in a 172, and my lessons were at an airport with a 5000’ runway, so there was a bit of wiggle room. And I’m sure there are different considerations for a single-engine piston than for a multi-engine jet, but I never did figure out the best practice for that situation.

C-172K, 5,000-foot runway. I always made ‘power-off’ (i.e., engine at idle) landings with 40º flaps. It was my dad’s airplane, and I wanted to save his brakes and make the mid-field turnoff.

@Robot_Arm: That “always be able to make the runway in a failure” idea was certainly the traditional 1930s way to teach aviation. And given the engine reliability of the day, not bad advice then. IMO it’s rather obsolete today for lightplanes, and fully inapplicable to multi-engine or fast planes. Let’s explore it a bit though.

IMO there’s a lot of old wives’ tales in GA training. Ideas are passed down from generation to generation without really knowing why they were ever invented, and therefore there’s no ability to think through whether they’re still applicable. They may be solving a problem that’s long since been solved by other better means. I think this is (mostly) one of those.

The idea does raise the question of “if I’m supposed to be in gliding range of a runway in the traffic pattern, how come it’s OK to NOT be in gliding range of a runway for all that time in cruise?” Hmm. No good answer there.

Some of the logic is that in cruise you should be high enough to have sufficient glide time to select a tolerable off-field landing spot, remedy the failure to the degree you can (change fuel tanks, fiddle with mags, mixture, etc), and also radio a call for rescue. At low AGL altitudes, there isn’t time for much except aim and flare, so best to make that a soluble problem by having a runway within your engine out glide range. Which really turns the emphasis of the rule on its head to say:

Always have enough AGL altitude so there’s a suitable landing spot within your current glide range. And always keep at least one selected, hopscotching along from takeoff to landing, and especially in cruise where you spend most of your time. When unavoidably at low altitude, that spot should be an airport if possible.

Now let’s talk just in the pattern …

Back in the day of Stearmans and Jennys, airports were square empty fields of grass or dirt ~1/2 mile on a side (hence the term “airfield”), landing rolls were a few hundred feet, and you were the only airplane in the sky. ATC had not yet been invented. Flying a box pattern around the outside of the field where at any moment you could nose down and turn towards the closest edge of the field and still make it was relatively easy. Nowadays in the pattern at a tower controlled GA field where you’re at 800AGL 5 miles from the runway turning downwind to base? Not gonna happen. Engine quits, you’re landing in the surrounding suburb or forest or whatever.

IMO this is why the maxim is obsolete. It simply can’t be implemented in most regimes of most flights. So the emphasis should be elsewhere. Such as how to select the least bad off-airport landing spot, having one of those always in mind, not running out of fuel, etc.


But that’s not addressing your original and completely legit objection:

If I maneuver to always be able to make the runway without an engine, then how do I avoid landing long with an engine?

The answer is simple: drag management.

An typical lightplane piston engine at idle at traffic pattern speeds produces net drag. The same engine failed produces more drag. It’s a bigger increment than you might expect, but it’s not night and day.

So in an old fashioned flapless airplane, the kind the advice was invented for, you …

Fly a tightish steepish pattern where you can turn towards the runway to shorten your path at any point. If the engine quits, turn directly towards the end-ish of the runway, planning to turn again to align with the runwaywhen you get closer. Now you’re probably high, so use a slip to steepen your descent until your non-slipped descent angle takes you to someplace well down the runway. Now stop slipping and glide 'er in. You aim maybe 1/3rd down the runway so it you misjudge that, you have room to come up short. IOW If you land shorter than you’d estimated, you’re still on the runway. And all this is for airplanes that need very little runway length to stop once on the ground.

In the traditional 1940s-1950s airport that had several runways arranged like a asterisk or pickup sticks, when you turn directly towards the field you may be well aligned with a different runway than you’d planned to use while power-on. That makes it even easier because now you don’t need a big turn at the bottom to align. You’re probably real high now. Jump on that slip until things look more normal, then finish the glide to this other runway.

If your engine is still running when you turn final for your original runway, now the problem is different. Your path to the runway is now as short as it can be. So plan to get there high / steep and use a slip to increase your drag enough to descend to impact at your aimpoint. Which starts out maybe 1/3rd down the runway and as you get closer, you move that back towards the threshold. If the engine quits, kill the slip and suddenly your drag is less and your glide is longer and you still make the runway.

Easy peasy. As long as you’re planning all the way around. Which again is IMO a bit silly in 2023. Or at least is often unattainable in 2023.

For one of those modern new-fangled airplanes equipped with flaps (and maybe even a sissy nosewheel :wink: ), the same idea as slipping can be accomplished with flaps. Take a look at the POH for any lightplane and you’ll see that while flaps reduce your stall speed, they reduce your glide ratio even more. If you’re on final with, say, half flaps and the engine quits, poke the nose down to pick up the 5 or maybe 10 knots/mph you need as stall margin, suck up the flaps and suddenly you can still reach the runway. If you’re already at full flaps, reducing flaps to half makes a much larger change in drag than it does in stall speed.

Said another way, the engine power you’re using on a normal flapped approach is at least partly being “wasted” just overcoming the flap drag. If you lose the one, then lose the other and now you’re back in balance and happiness ensues.

[aside]
In jets the problem is different, but a LOT of the reason for large landing flap angles is to create a LOT of drag to be overcome by a LOT of engine thrust. Not for the engine failure scenario, but for the sudden go-around scenario with engines that are inherently slow to accelerate.

With jets, faster the RPM, the faster the engine accelerates; it’s very non-linear, more like exponential. To boot, thrust output is also exponential on RPM, where the last 5% of RPM is 30% of the thrust. Back in the day, idle to full thrust was maybe 10 seconds, while medium power to full thrust was maybe 4 seconds. So approaching at medium power gives a safe quick go-around, and the flaps are sized so one can descend and hold speed with the power way up at “medium”. Newer engines accelerate quicker, but it’s still nothing like an ICE car or plane with negligible spin-up time.

Our go-around procedure is to shove up the power and simultaneously reduce flaps a bunch. The drag reduction happens much faster than the thrust increase does. In either case, that gets us going upward immediately while everything else catches up.

[aside 2]
In the F-16 we practiced engine failure approaches. You’d aim to arrive over the middle of the runway at 10,000 and 300 knots which was a comfortable glide speed. Assuming you got there, you’d start an immediate rather tight turn to a short downwind, which turn would scrub off speed to maybe 250, then hold that speed. Then another 180 turn to final, all the while aiming about 1/3rd of the way down the runway. Somewhere along the way you’d deploy gear which gave you landing flaps at the same time.

As the gear/flap drag came in and you steepened the glide to hold the 250, your impact point would move to about 1/2 mile short of the runway. You’d be jockeying how tightly you turned and how long on downwind to achieve that result. Once you were rolled out on final re-aim for partway down the runway and the speed starts falling off from 250 to the 150ish you want over the threshold. Then assuming your energy management was good, you run out of altitude and over the runway and plop it on. Better to be long than short. The baby wheel brakes aren’t great at stopping you, but the tailhook sure is. Conversely, the “fix” for too short was “Eject! Eject! Eject!”.

One last paragraph on the F-16 aside …

For practice we’d do these at idle with partial speedbrakes. That drag offset the idle engine thrust. And if the engine quit for real, just retract the speedbrakes and finish the maneuver. Same exact idea as the Jennys and Stearmans. And Cessnas and Pipers.

Use drag and energy management to run out of everything all at once just above the right spot on the ground. All else is just details.

That’s a great analysis of the problem. Let me just add a few comments.

My flying lessons were in the early 1990s. Not quite the fabric and tailwheel era. Considering 30 years have gone by, the engines and reliability probably haven’t changed much.

As for not being able to glide to a runway while in cruise, there’s nothing you can do about that. The impression I got from my instructor was that you can’t eliminate all risk, but while you’re in the traffic pattern you can give yourself a little more margin by flying the approach in such a way that you’re within engine-out glide of the runway.

As for managing drag and sideslipping as a routine part of approaches, I feel like that might create more issues than it solves. Every maneuver, or change in settings, has the opportunity to go wrong. A few posts ago, you described the goal of being on a stabilized approach for some distance before landing. I think that has a benefit in small planes, too. The closest I ever came to an accident was a flight where I got a little behind on the workflow and didn’t extend my flaps until short final.

I do find these sorts of discussions to be interesting. There’s a lot of old-time conventional wisdom in flying, and pilots (if I can still call myself one) don’t often go back and consider whether it still applies.

Agree that the 2020s and the 1990s and the 1970s when I was first learning are all about the same in terms of light airplanes, airports, engine reliability, ATC, etc.

My point was that the received wisdom is far older than that. Which is still somewhat wise even today, but is a lot more simply “received” than most folks stop to think about.

Also agree that there is a real tradeoff between doing something stable that has little change or potential surprises at the the bottom, but turns to shit if the engine quits, versus flying a much more dynamic, constantly juggling approach every time to guard against a (WAG) 1-in-100,000 risk. Or 1 in 20,000 or whatever.

In the case of jets, “stable” is defined as: fully configured, checklists done, on unchanging approach speed, at the correct and unchanging descent angle, on and tracking the centerline, aimed to impact at the right spot on the ground, and power stabilized at approach RPM. Our requirement in VMC absent windshear is to be “stable” by 500 feet, or ~25 seconds before ground contact. Things can be pretty dynamic upstream of there, but the funnel gets tighter as you go and all shenanigans are absolutely positively over by 25 seconds to touchdown. Or else go around.

In a lightplane, being fully settled down by ~25 seconds out is also a darn good policy. It’ll just be a bunch closer to the runway vertically and horizontally due to the slower speeds.

I heard a great story about a gathering of float-plane pilots. They were discussing which way to land on a flowing stream, depending on which way the wind was blowing. No one could agree, until an old bush pilot said “takeoff and land downstream.” They asked him why. He explained that if there were any tree limbs or other obstacles in the water, the current would bend them downstream. If you hit something like that, you wanted to skip over the top rather than get caught and pulled to a stop.

There’s a huge amount of flying lore like that. I find it all fascinating.

Well there’s the rub. I’m not too keen on landing on selected off-field landing spots. Almost nothing good comes of that. I spent a rediculous amount of time practicing emergency landings for that reason. If there are planes in the pattern I would play the game but given the choice I tried to set it up for an engine failure. That means engine-to-idle at small airports or once with no visible Plan B. If was a long runway I’d pick a spot further down. The last time I did it at a controlled air field I was pushing minimum fuel and didn’t want to find out the burn rate was less than optimal.

I wonder which way Philippe Cousteau was landing.