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A score and more years ago, “stable approach” came into vogue as an attempt to reduce airline accidents. Why? All those airline landing accidents came from unstable approaches, so unstable approaches must be the major causal factor, right? Over the years, the definition of unstable approach has morphed slightly, but “stable approach” persists as the Holy Grail of approach and landing safety, perceived as the one necessary and sufficient ingredient of a good landing outcome.
At the last gasp of the last millennium, I was hired at Boeing to devise an unstable approach monitor. Everybody, including me, “knew” that detecting the unstable approach and alerting the crew would reduce accidents. Simple, right?
My first step was trying to get a handle on unstable approach details, looking at ASRS reports on unstable approaches and on bad landings. I expected tight correlation. The first data set was a half dozen unstable approach reports, all of which landed normally. The second data set was a half dozen bad landing reports, all of which came from stable approaches. Hmm. Time to re-think the problem.
One red herring in the unstable approach discussion at that time was the fact that almost all airline landing accidents came from unstable approaches. However, by limiting the sample set to accidents (such limiting is called sampling bias), almost anything could be proven. For example, every one of the airline accidents were in monoplanes, tricycle gear, turbine powered, with multi-person flight crews. Nobody was suggesting that the solution to airline accidents was piston powered, single pilot, biplanes with tailwheels…
As is too often the case, politics was involved in aviation safety. Way back then, the Flight Safety Foundation was pushing the unstable approach concept, including the now-abandoned mandate of a go around if the approach was not stable at 1,000 feet IFR or 500 feet VFR. I was told that the Flight Safety Foundation was very political. And, of course, other organizations bought in to the unstable approach concept. I bought into it, too, until I saw the data.
Safety recommendations are not always rigorously grounded in data.
It’s worth noting in passing that safety recommendations and regulations too often reflect the personality, temperament, and preferences of the recommender/regulator and not the data.
Back to Boeing. I had unstable approach data from three sources: one was a loosey-goosey major US carrier, one was a highly disciplined European carrier, and the other was a mixture of US major carriers. Their unstable approach rates were 15% at one end and 1.5% at the other. In other words, even the very best carriers had an unstable approach rate of 1.5% and, of course, their accident/incident rate was nowhere near that. Another data source indicated that fully half of the unstable approach accident/incidents were high and/or fast at the final approach fix, so in those cases, unstable approach was a symptom, not a cause.
“The Myth of the Unstable Approach,” available online, documents what I found in the data: that stable approach criteria did not usably predict bad landing outcomes. Back then, when I sent my findings to the Flight Safety Foundation they did not even reply. Fifteen years later, another report came out recommending that 300 feet be the go around altitude decision height, not 1000/500 feet.
Even today, accepted reports state that only 3% of airline unstable approaches result in go arounds. The unthinking assumption in those reports is that the unstable approach concept is unimpeachable, and so the go around rate should therefore match the unstable approach rate. Few seem to consider that the data show the 3% rate indicates that unstable approach criteria don’t tell the whole story.
An important point: to be completely clear, a more proper term is “unstable final approach,” not unstable approach. In VFR general aviation landings with a traffic pattern, or in an IFR circling approach, or in discussions of the topic in general, let’s clarify our thoughts by deliberately including the middle word—“final.”
So here’s the question: for us general aviation pilots, since unstable approach doesn’t completely describe reality in the airline world, which if any of the unstable final approach concepts apply to general aviation?
So What Is a “Stable (Final) Approach?”
Stable (final) approach criteria—there are variants—require airspeed, vertical speed, glideslope deviation, and localizer deviation all being within certain tight limits, gear and flaps set, and an approach briefing given. Including an approach briefing is an obvious appendix to “stable” approach, which might more properly be called a “proper” approach or something like that. Later stabilized final approach definitions included thrust steady and all callouts given by the pilot not flying, and in some definitions, the absence of large or abrupt control inputs.
This whole class of stable final approach definitions has obvious shortcomings for rectangular traffic patterns commonly flown by VFR general aviation.
The Basic Premise
The basic premise of the stable final approach concept is that stable final approach and good landing outcomes are tightly correlated. Thus, any unstable final approach means that a bad landing outcome is highly probable, and the aircraft should go around. Often implied—but not stated—is that if the final approach is stable, the approach can be completed to touchdown, regardless of what else may occur.
We’ll examine this idealized over-simplification in detail, below.
Flight Dynamics
First, we need a little bit of engineering terminology—sorry. The term we need is a state variable of a system. To simplify, a state variable (airspeed, bank angle, position) is a variable in which it doesn’t matter how the current value was achieved, only what the current value is.
The airplane is on speed and on glideslope over the runway—does it matter how it got there?
Here’s a simple example. Your airplane is in its tiedown location. It doesn’t matter whether it taxied in after a 200 nm flight or was towed there after maintenance; all that matters is where it is. Position is a state variable.
There is another definition of state variable in the context of matrix representations of linear differential equations, but that’s not relevant to the present discussion.
Back to flight dynamics, with a touch of over-simplification. The aircraft three-dimensional position, velocity, and acceleration are all state variables. Similarly, the aircraft three-dimensional attitude (including heading), angular rates and angular accelerations are state variables. In other words, from a state variable point of view, it doesn’t matter how the airplane got there, only where it is.
Yes, there can be aerodynamic effects which challenge the state variable simplification. However, for moderate maneuvering and control inputs in general aviation airplanes, those effects are safely ignored, as any such aerodynamic effects are mild and short-lived.
As described in “The Myth of the Unstable Approach,” the whole point of the approach is to get the airplane ready to flare properly, with all of the state variables—all of them—where they should be. Because those are state variables, it doesn’t matter how the airplane got to the correct start of flare, only that it did get there.
In other words, from a purely state variable/flight dynamics point of view, stable final approach is irrelevant. There is, of course, a whole lot more to the story. (Remember that we’re discussing all of the state variables, including the rates and accelerations, not just some variables.)
Wait a Minute!
It’s all fine and good to talk about stable final approach criteria, and getting the plane ready to flare, but did you notice the disconnect? Stable final approach criteria are always given as an altitude above which the approach “must” be stable, but final visual alignment to get to the start of flare is below the stable approach criterion altitude. As the airline data showed, stable final approach criteria can be so far in advance of touchdown as to be poor predictors. And that evidence invalidates the premise of stable final approach.
Going back to the Boeing research, accident data showed several events where there was a marked meteorological shift at 300 feet. Several approaches that were completely stable above 300 feet came to grief in adverse meteorological conditions below 300 feet. Again, inconsistent with the premise.
A factor to consider, then, is at what altitude can an airplane, airliner or light plane, repeatedly and safely recover from an “unstable” approach and go around? In light planes, it’s easy for a reasonably skilled pilot to recover from an approach that’s not perfect at 300 feet (more than half a minute at 500 ft/min descent rate), or at 30 feet or 3 feet, or after a bounced landing, and plenty of time to screw up an approach that was perfect at 300 feet. And general aviation pilots regularly handle gusts, even in the flare.
An interesting aside is the performance of the earliest airline jets. Way back when, I recall reading that if the runway environment was not visible at minimums, like 200 ft. on an ILS, it was mandated that the missed approach procedure be executed, even if the wheels touched the runway on the go around.
Where Does Stable Final Approach Make a Difference?
An instrument approach in a jet and a short turn to final in a crop-duster are not the same.
So how does the pilot get the airplane ready to flare, with all—all—of the state variables where they should be? Not just flying through an imaginary stable approach gate, but with the airplane aligned in pitch, roll, and heading, airspeed and vertical speed as desired, ground track along the runway centerline, and with all the velocities and attitudes constant.
Even if the state variables don’t care how the airplane arrived at the flare, the pilot needs a certain amount of time to verify that all the state variables, all those the velocities, rates, and accelerations, are where they should be, so as to have a feel for what the airplane is doing to make it easy to flare. So how to measure the time available before touchdown?
Turns out that time to touchdown on an approach is easily approximated using height above touchdown when the airplane is descending at a more or less constant vertical speed. That’s one reason why stable approach criteria are specified in terms of altitude, even though time to touchdown is what really matters, whether on a normal approach, a shallow approach, or a steep approach.
In calm air, a more proficient pilot might be able to correct all of the state variables at the very last second before touchdown after an aggressive or wobbly short final, but in gusty crosswinds or in an unfamiliar airplane or when under stress of whatever kind, the pilot will need time to get the flight path under precise control.
Consider crop-dusters, highly proficient and well in tune with their aircraft. The few videos I found online showed base to final turns at 200 ft., meaning that the final approach segment was very short.
Regular GA pilots on the one hand and crop-dusters on the other indicate that “one size fits all” should be examined very, very carefully for stable final approach.
An Insignificant Factor
Although not part of the conventional, flight path parameter definition of stable final approach, final approach should be of long enough duration that the pilot can adjust not only to the winds and gusts, but also to any transition to a new sight picture.
Those who have flown instrument approaches and suddenly broke out of the clouds, or taken off the hood, have probably experienced a momentary feeling of not being with the airplane and needing a second or two to get a feel for what the airplane is doing. This same phenomenon can occur with autopilot disconnect. In those cases, even if the airplane is on a perfectly stable approach, the pilot needs a moment to catch up to the airplane. How long that takes will depend on numerous factors: proficiency, time in that particular airplane, currency, experience, IMSAFE, and such.
My hunch is that this factor is never discussed because it is quicker than the time required to estimate winds and gusts, and that this factor diminishes with highly experienced crews. (We’ll ignore the special cases of CAT II and CAT III approaches.) And the unstable approach concept started for highly experienced airline crews.
Airliner vs. General Aviation Criteria
Not all airline practices translate well to GA flying.
Some folks argue that because the airlines have 1000/500 foot criteria, so should general aviation. Let’s look at how well those parameters transfer. (By the way, one major US airline with a solid safety record, flying into very challenging terrain with often terrible weather, does not have any unstable approach criteria.)
For our first criterion challenge, consider time to touchdown. If both the airliner and the GA airplane are flying a 3-degree glideslope, one at 140 knots and the other at 70 knots (just to keep the math simple), from 1000 feet it will take the GA airplane twice as long to get on the ground. Or, to put it another way, if time to touchdown is the stable approach criterion, a 70-knot approach speed would indicate 500/250 foot unstable approach criteria. And remember that the recommended airline go around decision altitude was reduced to 300 feet, which would translate to 150 feet.
(If I recall correctly, the Private Pilot PTS used to require the airplane to be established on final no closer than a half mile. With a 3-degree glideslope, that is 150 feet.)
For the second criterion, consider maneuverability and responsiveness. Without getting into a whole bunch of flight dynamics engineering-speak, consider the analogy of a city bus versus a sports car. The sports car can maneuver much faster than the bus. In the same way, a small plane needs less time to get lined up on a desired path, hence, less altitude. This argument can be formalized by comparing stability parameters and time constants (engineering-speak), and time for the engine to achieve full power, but we’re not going there.
As mentioned above, some later stable approach criteria consider large or abrupt control movements or power changes “destabilizing.” By that standard, many light airplane approaches are unstable on short final due to thermals, downdrafts, gusts, or changes in wind direction at low altitude. However, light planes in general can more quickly respond to displacements from a desired flight condition and can handle those changes more readily and so can safely fly with attitude displacements and power changes that large jets cannot. For light planes, what happened at a thousand feet—minutes ago—makes little if any difference right before the flare.
It’s also the case that airline operations reduce risk with highly proficient pilots, well-defined procedures, and with repeatable, well-structured operations. The smorgasbord of general aviation accepts higher risks to allow more kinds of pilots to do more things in more kinds of planes in more circumstances. In that sense, general aviation often discards the perceived security blanked of stable final approach for greater utility.
Miscellaneous Details About Stable Approach Criteria
Many of the airline-centric stable approach criteria have, as the last item, that an approach briefing was carried out. This makes a lot of sense when flying IFR, whether GA or airliner. And for GA, most of us will at least subconsciously consider winds, runway length, desired turnoff, and all those factors when making our first landing on a runway. But flying closed traffic, it’s dollars to doughnuts that subsequent landings will not be individually briefed. Theoretically, then, those later approaches are “unstable.”
Airline pilots are presumably highly trained and proficient, so stable final approach criteria don’t consider proficiency explicitly, except for pilots new on type. Fatigue on long haul flights can affect piloting skills, but discussions of airline pilot fatigue do not seem to be reflected in stable final approach criteria.
The familiar 500-foot callout has even made its way to iPad apps.
In my experimental RV-9A with a glass cockpit, I always get a 500 foot aural callout in the pattern, regardless. When I get this callout on base leg, about to turn final, this annoyance declaims that I had better be nicely established on final. That callout is also a reminder of backroom mischief at the FAA way back when. Seems as how one faction, let’s call them the unstable faction, wanted a 500 foot callout to be in the FARs for airliners, and another group said no. Seeing as how changing the FARs was a really big deal (still is—that’s why LSA specs are not in the FARs), the unstables realized that their way forward was to modify the TSO for hardware required by the FARs, and they got away with it.
Lastly, there are some airports with 800 foot traffic patterns and some with very tight traffic patterns, for a variety of reasons. At AirVenture Oshkosh, landings on Runway 27 require “unstable” approaches. The point is that general aviation aircraft can exploit maneuverability for greater utility than larger aircraft, and that this greater utility is performed with different safety criteria than larger aircraft.
What About Decelerating Approaches for GA?
It’s time to re-examine old ideas and old assumptions.
Traditional stable final approach concepts focused on one jet airliner at a time, and did not consider airports that served airplanes with a wide range of approach speeds. Decelerating approaches facilitate that mix of approach speeds.
For example, sometimes at busy airports, a slow airplane may be asked to keep speed up as long as possible to fit in with jet (airliner) traffic. In my RV-9A, given the choice, I’d prefer to fly the ILS at 100 knots. ATC does not always appreciate that with 737s behind me, and I’ve flown approaches (VFR) as fast as 160 knots. Conversely, if I’m following a flight school Cessna 172, I might need to slow down 20 or 30 knots.
Sometimes it’s not even that simple. On the most recent LPV approach, ATC requested me to speed up outside the FAF, but after I was handed off to tower, they asked me to slow down.
It’s also worth re-examining the value of a constant speed final approach for a GA airplane, starting at outside the final approach fix. What does it buy you, besides extra workload, to fly final approach airspeed very precisely at a distance from touchdown when there is plenty of time to slow down? For example, at Prescott, Arizona (PRC), the ILS has a procedure turn. In my old Cessna, an 80-knot approach speed and a 20-knot headwind meant a ten minute ILS!. A decelerating approach would have been a more efficient use of the airspace.
Here are the details on how I do a decelerating approach in my airplane with which I’m very familiar and in which I’m very proficient. I’ve flown decelerating approaches in many other airplanes, but with differences in the details.
Working backwards… I want to be at minimums at 80 knots with flaps 10 degrees. This is, no surprise, the go around decision point, to expand on the word “minimums.” With the longer runways that come with instrument approaches, it’s easy to slow my airplane to 70 knots and full flaps and land with tons of runway remaining. I practice it all the time.
It’s also easy to go around at 80 knots with 10 degrees of flaps from minimums. But since my plane is an experimental, I had to figure out what worked for the airplane and for me. When I was new to the airplane, I tried go arounds on autopilot from 70 knots and full flaps but too much happened too fast, with lot of power and too much nose-up pitch before the airspeed could build. Now, I’ve adjusted the autopilot pitch for a nominal pitch on the go around. Once the go around is established, flaps up and airspeed building, I can change the autopilot from go around pitch to preferred climb at 110 knots.
A decelerating approach in an airplane you know well makes a lot of sense.
For me, on a decelerating IFR approach, I want to be stabilized—yes, I used the “S” word—at 80 knots and flaps 10 degrees, 10 seconds before minimums, so that I can have a good intuitive handle on the situation when I transition from IMC to VMC. In other words, that very brief stable final approach makes it easier to make a good decision on go around or not.
If conditions are less than optimal, I want more than 10 seconds. How far out I have to start slowing down depends on whether I’m flying my own speed or helping ATC by flying final at a higher than normal speed. (As an aside, US Navy jets landing on a carrier fly an 11-second final approach path, from when they intercept final approach on altitude, on centerline, configured and on speed.)
Yes, ATC speed requests are often specified as speed until the final approach fix, but I’ve got to believe that if they ask for maximum forward speed, they really want it as long as you can do it.
The bottom line is that if you have a plane with a landing speed substantially slower than the jets, and you want to share the air with the jets, learn to do decelerating approaches that transition to stable final approaches close in. They’re easy to learn, easy to fly, and are as safe as conventional stable final approaches.
How to do it? The decelerating approach starts with a constant power descent. At an appropriate distance from the go around point, easily estimated from height above minimums, reduce power to the setting for a normal speed approach and fly the glideslope with pitch only. When the airplane has slowed to normal approach speed, continue the approach using standard pitch/power techniques. This is less workload than trying to precisely maintain glide path and airspeed all the way down. Estimating the time required to decelerate comes with practice, with no penalty for slowing down early. (It works almost as well to use height above touchdown instead of height above minimums.)
Stable final approach from 1000 feet with jets behind you? No way. The FAA, training organizations, the books, and most social media influencers are behind the times on this one. Decelerating approaches are the easy way to go for slow airplanes with good handling and performance characteristics.
So What?
Circumstances permitting, are stable final approaches desirable? Of course.
Are the 500/1000 foot stable final approach criteria always appropriate for light GA aircraft as go around decision points? No.
Mixing in with jets? Decelerating approaches are the way to go.
For general aviation, go around criteria are the real issue, not a stable final approach. The airline organizations finally came to a similar conclusion just a few years ago. It’s a topic for another day, but not only should we GA pilots practice go arounds from final approach, we should be proficient in go arounds from every point in the traffic pattern, including base-to-final turns at low altitude.
Are there appropriate go around criteria—not stable final approach criteria—for general aviation? Yes. Should approach criteria for light GA aircraft vary with whether the pilot has his head in the game, is having a good day or not, vary with the weather, gusts and winds, the runway, day/night, IMSAFE, proficiency in that particular airplane, experience, and a host of other factors? You bet—just like personal minimums, except that go around decisions are made at the last second, not during preflight planning. And for general aviation, with faster response times than airliners, go around criteria are best measured much closer to touchdown, sometimes even in the flare—or even after a bounced landing. (We’ll ignore single-engine approaches in twins, with different considerations). And remember that personal minimums are primarily for flight planning. If conditions have degraded below personal minimums during the flight, and there’s no alternate, then the pilot must land, regardless of personal minimums.
Here’s another way of thinking about it: stable final approaches for general aviation are justified mostly by tradition, not by operational reality.
Lastly, no arbitrary approach criteria for general aviation will remedy deficient pilot skills.
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I agree that stabilized (final) approach criteria can limit an aircraft’s utility, but isn’t that kinda the point? All pilots—but especially new pilots, rusty pilots, or pilots flying in an environment they have never experienced—should establish and follow personal minimums to simplify decision making. I include stabilized (final) approach criteria among my personal minimums because I believe they provide me the best opportunity to see a situation developing that might require a go-around. When I’m flying around the homedrome I give myself a bit more latitude, but if I’m flying to an unfamiliar airport for the first time I believe establishing stabilized (final) approach criteria gives me the best opportunity to avoid a landing mishap.
In short, personal minimums are meant to specifically limit the utility of an aircraft in the pursuit of safety. At least that’s the way I see it.
Thank you for the article, Ed. From reading it, I realized I had some time ago subconsciously dismissed the “stabilized approach” concept (as usually contemplated) in my piston single. I fly tight traffic patterns while VFR and am a fan of the decelerating approach while IFR, so the airline-centric stabilized approach definition had little practicality for me. I do, however, have a good sense of what looks and feels right, and have also experienced the phenomenon of a bad (final) approach resulting in a bad landing. I like the idea of re-introducing myself to a stabilized approach check around the 150′ to 300′ mark–enough time to double check I’m configured, airspeed is where I want it, I’m lined up, and I’m not diving for the runway or dragging it in.
I agree. Dragging the CJ3 in at 100 kts from a faf just doesn’t seem natural after awhile. I often do decelerating curving VFR approaches as well if there are no traffic issues. In the jet, I want a couple/ three hundred feet or more to line up, feel the crosswind and kill a drift but don’t need minutes of it.
Ever watch yourself or an autopilot fly an ILS on a windy day? Often there’s not much control movement until down near the ground due to wind gradient and turbulence from ground objects. Correcting for that isn’t helped by flying the last 3 miles stabilized.
Night is a different matter.
Ed, it “sounds” like from the article you were trying to train a binary classifier (stabilized vs. unstabilized approach). Is that right?
This was a great article btw. What I took from it was that we as GA pilots really need more practice during the last 300 feet down!
As a corollary: What is the purpose of an IAP? To land? No! To put you in a position to safely land – visually!
A Well written discussion. I particularly enjoy when close analysis of data shows many paradigms to be just wrong. ‘Intuitive’ or ‘obvious’ criteria often fail the reality test. I particularly like your State-Variable approach to the problem. As a pilot preparing to land, we are consciously and subconsciously getting those variables where we want them. The most basic is configuration which is fairly straight forward. If we can’t get those criteria right before touchdown we go around. Dealing with crosswinds and gusts on short final is mostly a proficiency issue. Again if you know what state you want to be in, your proficiency will allow you to get the airplane to that state. Or, if you cannot, you go around again. The whole concept of ‘saving a landing’ is really a last seconds attempt to get those state variables where you want them. The better the pilot, the later that can happen. A stable approach won’t guarantee a good landing (plenty of data on that) and an ‘unstable approach’ by the current definition doesn’t preclude a good landing (your data clearly shows that). A pilot can choose to abandon an approach at ANY point. She shouldn’t wait until a magic altitude to finally throw in the towel. Getting behind the airplane can happen at any point and that’s when to act. Thank you for showing how the politics often exceeds reason.
Thanks for debunking this myth of the stable approach. Flying a light GA plane in Texas for the past 40 years, I can count on two hands the number of times the winds have permitted anything that might be considered “stable”. I often wondered if the FAA official who invented this mythical approach had ever even been in the cockpit of a small plane. Even in my slippery Mooney, I just try to get close to the target airspeed and altitude until I cross the numbers and get out of the eddy currents and convections and can finally get “stabilized” in the flare. Anyone who thinks differently should come to Texas in the summer and show us all how it’s done :)
Dave; You hint at the concept of a stabilized “flare”, not a stabilized approach. In my RV7, I like keeping the airspeed 10-15 knots high, especially in gusty winds, to all me to make the runway if I lose the engine on short final. This is a concept I used flying gliders that also provided compensation for higher than anticipated headwinds on final and fits in well with Ed’s decelerated approach concept. BTW, using 500′ as an altitude to be stabilized at in a light aircraft means your final is 1.5 miles or more longer (300′ @ a mile is optimum) and really gums up the pattern on a busy day.
Great analysis, however the crux of the problem, imho, was touched on briefly in the last sentence. Proficiency is the key to the landing accidents and incidents GA experiences daily. Crosswinds, gusts, and simple aircraft control challenge the average GA pilot.
Good article, thanks for explaining a complicated subject in such a clear manner.
FYI, I find the 500 foot call on an IFR approach a good way to keep me aware/remind me of the landing elevation since I quite often fly to unfamiliar airports that are not sea level.
Well said Ed, I’ve been teaching your thoughts along with some of my own in the 121 arena for many years. Myself as a RV owner I’ve adapted the stabilized “slow down” technique to my procedures to mix with various other types of traffic. My airport, everything from Trikes to corporate jets, you have to try and mix in . Ears and eyes to your surrounding traffic. Thanks again for the work you have done and continue to do.
Ken
Not withstanding the noteworthy points in the article, as a CFII I liken the stabilized approach to picking favorable conditions for first solo flight–an attempt to minimize having to react to variables/unfavorable conditions. Being on speed, altitude, power, descent, and configuration positions the pilot ahead of the power curve, so to speak. Especially for the less proficient student & rusty pilots, establishing a stabilized approach early on minimizes workload. Just as important, a stabilized enhances one’s opportunity to scan for traffic, analyze wind effects, etc..
With all the emphasis on the “stabilized approach” the FAA does a poor job defining what a SA actually is and that is probably precisely because a one size fits all doesn’t work. As an active CFI, I have developed and teach the 4A concept to a SA. Airspeed, Alignment, Altitude and Attitude (flap configuration) so a Vref landing can be made to the first 1/3 of the runway. The go around point is dependent on aircraft type and pilot proficiency.
Good analysis…agree it’s really time available to fix any issues vs time required to fix it…that’s where proficiency matters.
Like your bus vs sports car analogy always thought it was silly to teach rowboats how to moor like a supertanker…unless that’s what your goal is (not the CFI’s!!).
OBTW…unless a few of my grey cells went UA, groove length at the boat is 17 seconds…time between acft is 50-55 seconds. 500 KIAS break at the bow to on-speed at the groove is one way to show your shipmates what you’ve got (or don’t…fame and infamy are only separated by a few letters).
Good article. Just a small gripe, with an acronym, especially in a technical article, please put the definition after the first use of the acronym.
GUMPS, gas undercarriage mixture props switches…
It took a while to figure out IAMSAFE, as that’s the appropriate thought process you should consider before going to the airport.
Let’s just stop the mnemonic poisoning. I put fuel in my plane, drop the gear, but I’m supposed to use gas and undercarriage when it really counts? Then there are about 25 more that are so arcane I need to have a translator to figure it out.
Ed,
Over 10 years ago we corresponded by email about the Air Cam. I dropped the ball and ignored your last email to me. I am sorry that I did.
When I noted the author of the Air Facts article it reminded me of those pleasant exchanges.
Thank you for publishing a great piece. It is inspiring meaningful discussion of the Cirrus Owners and Pilots Association site.
Sincerely,
Clark Jernigan
Spot on article. Worked for me for years flying a Baron into LAX with no complaints from anyone. No wasted time and access to better ground services mixing it up safely with the big iron.
Ed, spot on! Anytime someone tells me there’s only one correct way to do something I’m suspect as they most certainly are wrong. That said the teaching of primary students is best when simple constructs and guidelines are used. This shouldn’t be carried on indefinitely, remember a pilot’s license is a license to learn. I’m rarely a pattern flyer, I got my Mooney to go places. It was critical for me to learn how to keep my speed up flying into busy airspaces. One of the most important tools I had to self teach was how to bomb in and slow down just before the FAF. No CFI thinks this is good but reality rules in the NAS (National airspace for the person who requested acronym definitions). Far better to become proficient at going fast under non-stressful conditions so as to not be uncomfortable or “unstabilized” when the need arises.
I still get thrilled here and there for some of the authors and articles we see here at Air Facts, and you and yours is certainly one of those. The stable approach criteria is a law (“as certain as gravity”) in many airlines and the lack of correlation of it with good landings is puzzling, but then again you show exactly and clearly why. Nevertheless, like you said, it is like the 1500 hours rule: politics finding the right solution to the wrong problem (or the other way around – since both have worked in indirect ways – this deserves an article in the future). Specially now I am on the verge of falling back to a more often beloved GA flying than in the last thousand hours, it was a very insightful read! Thank you for that!
Good article. Ninety-nine percent of my time were hours at a major airline. I know very little about GA but I can see how the stable approach criteria may not fit as well in a Mooney vs a 757. I can attest however that stabilized approaches have been a benefit to safer operations at 121 carriers. I’m a believer in the practice.
Often approach controllers at a busy airport will issue the same “170 to the marker” instruction to a Navajo that they would to a 737. The safest thing is to not accept a speed to the marker above your maximum gear extension speed.
That way once you are close talking to the tower you can dump your speed and stay on track.
Great Article! As a 31 year major airline pilot I thought all my career the”stabilized” approach was thought up by a bunch of pilots flying a desk, in which case is understandable and works well. It fits in with “I fly the same when it’s clear n a million as when it’s 200 n a1/2”. If there were no ATC or other traffic my desire is to leave 30,000 ft at no sooner than 90 miles from touchdown, idle power, power up at 500 ft, “flair” ,idle reverse. Nice job Captain.
Unfortunately in today’s aviation training environment, most instructors are basically afraid of the airplane when they are close to the ground and don’t teach true basics! The student isn’t taught to think and fly and only know to do certain things at certain times and if they don’t follow those exact procedures then the approach is unstable and must be abandoned!
The airplane doesn’t have a brain and doesn’t know how high it is! Can we bank the airplane 45-60 degrees in the pattern? YES!! As long as we maintain the 2 most important things in aviation… AIRSPEED and COORDINATION!! Unfortunately coordination isn’t emphasized in the majority of schools today. From the start I teach how to arrive at the position of being ready to level and flare from a multitude of situations so my student can THINK n FLY!
Like the author said, look at a crop duster! Does that pilot do what he does close to the ground by magic or by maintaining the simple basic principles of airspeed and coordination!!
I am a retired airline pilot and I am 100% in agreement with your conclusions. I demonstrated in the 757simulator a VOR (do the airlines even have these anymore) approach that was angled 15 (or so) degrees off runway center line. I was able to safely arrive in the slot despite breaking out at minimums and with a ten knot tail wind. My ‘stabilized’ portion of the approach was the last three hundred feet from the runway.
Thank you for an excellent article. One of the problems I constantly encounter when training new CFIs is just how much incorrect information has been accepted and assimilated as “true” without any questioning of its validity. “Is it true,” is one of the most powerful questions to spur learning I have yet encountered.
I recently had a discussion with a CFI candidate who had just transitioned to the King Air C-90 and is operating it out of our rather small airport. He is the master of the 10mi straight-in because, “It is a stable approach.” I suggested that the continuous turn to final might be a stabilized approach as well because the accelerations remain relatively constant and the rate of change of velocity is smooth and predictable, resulting in the aircraft achieving landing state, i.e. position, velocity, and acceleration, at the correct point on the runway. He disagreed. Only unaccelerated flight to the point of round-out is a stable approach, to which I pointed out that the round-out is a turn followed by a steady acceleration wherein velocity is constantly changing and hence not stable by his definition.
In the end, the only point at which the approach must be “stable” is a few milliseconds before touchdown. This just serves to support the concept that all flight is dynamic and is nearly always in some form of accelerated flight. The pilot just needs to know what the maneuvering limits are at every point so as to be able to determine if the near-term desired outcome is achievable.
The current stable approach doctrine for GA never made sense to me. This outstanding article lays out why. When training new pilots, it is upmost important to get them to be aware of thier aircraft’s “state variables” and how to control them. Have been asked many times by different controllers whether I(we) could do a short approach or keep the speed up. Of course one can always decline those requests, but having mastered controlling the “state variables” and after practice with a competent CFI one should easly accomplish those requests safely. Short approaches (Power Off 180 degree Accuracy Approach and Landing) are a requirement for the Commercial certificate. Good to teach for the Private in my opinion.
I agree with and appreciate just about everything in this article. I’d explicitly add that the stabilized approach is a great training tool regardless of statistical correlation to accident rates. IMHO it’s more of a measure of a pilot’s skill in not over-controlling and setting everything up for success given current conditions. As a new pilot, when I notice myself on an unstable approach, it prompts me to do an internal check, “am I over-controlling and if so why?” Maybe it’s fatigue and that may be enough reason for a go-around to give myself a minute to perk up for a better landing.
Confused? Large airliners fly ILS with all engines and full flaps to mins. General aviation single and multi-engine light twins do not, they use approach flaps. So you had a stabilized approach to minimums, runway becomes visible, and what does most pilots do-they put in landing flaps! As the author mentioned, now you have to re-stabilize to land before landing.
There you go again Ed, making sense. You have eloquently reviewed the “stable approach” concept for light GA, and with your speed discussion highlighted the difference between checkrides and practice for transport category aircraft operations.
I always look forward to your discussions, recently my favorite was your thoughts about teaching pilots to overshoot final, so they can experience what it looks like and learn to make good decisions about how to continue without getting into a cross controlled condition – I think this article is at the top of the list now. Thanks for your thoughtful insight.
Every set of comments has to have one out-of-the-box (idiot) commenter. So here’s one: stop using Word spellcheck for your editor. You exchanged “almost” and “always” (both valid words, but the wrong one was selected) and you have an extra “was” in your text (best deleted, meaningless and confusing as it appears). The absolute best way to edit? Read the entire article, every word, aloud to yourself – the brain will pick up all those errors.
Now back to intelligent comments.
Richard Tamir