Stable Approaches

Bob Turner

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Here, an engine failure a half mile west of the airport will probably be fatal. The last two I am aware of were. There is no place to go. Roads are jammed with cars, and some of them have cute little kids inside. A nose-over is expensive these days, but at least you can have a margarita after you tow the thing out of the field.
 

Bartman

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I just completed my CFI recertification training (American Flyers) for the umpteenth time and had some material from the class that was still handy to throw out for discussion. The FAA's textbook answer for a stabilized approach for piston aircraft is described in: Airplane Flying Handbook Chapter 9: Approaches and Landings


An excerpt from this link:

Pilots may consider the following elements when attempting to set up and fly a stabilized approach to landing. The pilot should focus
on the elements that lead to a stabilized approach rather than the order of the elements or the insistence on meeting all of the approach
criteria. For a typical piston aircraft, an approach is stabilized when the following criteria are met:
  1. Glide path. Typically a constant 3 degrees to the touchdown zone on the runway (obstructions permitting).
  2. Heading. The aircraft tracks the centerline to the runway with only minor heading/pitch changes necessary to correct for wind
    or turbulence to maintain alignment. Bank angle normally limited to 15 degrees once established on final.
  3. Airspeed. The aircraft speed is within +10 /-5 KIAS of the recommended landing speed specified in the AFM, 1.3VSO, or on approved placards/markings. If the pilot applies a gust factor, indicated airspeed should not decay below the recommended landing speed.
  4. Configuration. The aircraft is in the correct landing configuration with flaps as required; landing gear extended, and is in trim.
  5. Descent rate. A descent rate (generally 500-1000 fpm for light general aviation aircraft) makes for a safe approach. Minimal adjustments to the descent rate as the airplane approaches the runway provide an additional indication of a stabilized and safe approach. If using a descent rate in excess of 500 fpm due to approach considerations, the pilot should reduce the descent rate prior to 300 ft AGL.
  6. Power setting. The pilot should use a power setting appropriate for the aircraft configuration and not below the minimum power for approach as defined by the AFM.
  7. Briefings and checklists. Completing all briefings and checklists prior to initiating the approach (except the landing checklist), ensures the pilot can focus on the elements listed above.

thanks for sharing that. What it leaves out, and what it is that allows us to adapt it to our procedures, is that it doesn’t specify the point in the approach by which we need to be stable. Different planes have different needs. IMHO, if we could be in a position to land using a glide path that is normal for our planes by 200’ AGL, we would be doing ok.

Teaching students that planning their descent to achieve this “stable” state just means that the improvisations we do to get down shouldn’t be continuing all of the way to the runway and that a go-around is the result of good decision making.
 
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Bob Turner

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The AIM says be established on final a quarter mile out. That is roughly 200 feet.
 

Goodyear

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I was taught that while in the pattern you must be close enough to make the runway if the engine quit. If the engine quits do Citabrias glide at 3 degrees? No. They glide more like 7.125 degrees. (8-1 glide ratio). So to meet the definition of stabilized approach on a 3degree glide slope you would dive down to intercept it at about 200 feet of altitude. what speed would you need to intercept 3 degrees on final and maintain 3 degree glide to the runway? (Which will probably stall the airplane at some point).This sounds to me like the most unstabilized and difficult approach you could imagine. Altitude is safety, most of my approaches are probably more like 7-10 degrees. 700-1000 ft/min consistent descent at 60 (often slipping). Seems stabilized to me. I don’t really care about 3 degrees unless I’m shooting an approach in a high performance single.
 

Kel

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If the FAA says to jump of the bridge...
Don't let them run you down a rabbit hole. It may be simpler to think of it (outside of FAA check rides) as being squared away early, such that the minimun number of adjustments are required until the round out?
 

darrell whitley

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We always said fly it the way the check airman or FAA said. We also said to fly it like you were always getting a check ride. Standardization in those days was the key to success.
A single engine aircraft is somewhat different. The difference might be the strips you land at, and the fact that if you lose the engine on takeoff you land straight ahead unless you have enough altitude to turn back. Either way you’re going down!!! Same on landing.
 

Bob Turner

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The idea of a two mile 3 degree power on approach (VFR) in a Cherokee is relatively new. Nobody learns power off approaches any more; the flight school instructors ask for short approaches and we watch in amazement when they go a mile beyond the runway to turn base.
And then, several years ago, the DPEs extended that idea to Champs and Cubs.
Do what the DPE wants, but at crowded airports, avoid the temptation to fly like you were on a checkride. Rod Machado says 83% of collisions in the airport traffic area are a faster aircraft overtaking a slower one on final.
 

Godzilla

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It’s really sad students don’t learn power off approaches any longer.
Power off from abeam downwind was a cornerstone of airmanship when I learned to fly in Champs and Citabrias.
At sixty five mph after closing the throttle in my Champ the flight path was completely stable except for maybe a little slip to get rid of a little excess altitude. Probably a little in excess of 3 degrees though. This technique definitely teaches a student how to manage energy.
 

Bob Turner

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Nice to see you resurrect this after a year and a half.

We are now officially the world’s busiest GA airport. The Cubs and Stearmans, and indeed two of the Decathlons, now enjoy an “inside pattern.” We practically get an automatic clearance for “early turns and short approaches.”

It doesn’t hurt that one of my Cub students is a senior controller.

We have yet to get a definition of “short approach,” but when they squeeze us inside a fast-moving Cirrus on a 1 1/2 mile final we know what they mean.

The idea that an engine can quit at any point is emphasized. Our “inside pattern” is driven with that thought in mind. It pays off; the 220 Stearman had several partial engine failures before rebuild.

Most of us could manage an engine failure in a Cherokee six - but a recent Friday discussion, beer in hand, reveals that the average Cherokee Six checkout does not include a power off approach “because they are so scary.”
 

Desert7GCBC

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I've done three forced landings since the 70's. Two were engine failures in the pattern in my Citabria. Luckily, both of them happened when I reduced power on downwind. In both cases, I was able to fly a tight pattern and didn't have to sweat stretching a final approach. (One involved the idle screw falling out of the carb and the other involved both mags being burned and shorted internally due to two spark plugs with infinite resistance. Run-up mag-check was normal.) Incidentally, in the lost idle screw situation, I found that the engine would run in a somewhat herky-jerky manner when pumping the throttle. That might be useful to stretch a glide a bit if necessary.

Alas, it's mostly not possible to fly power-off approaches at my home field anymore due to the opening of a busy flight school. Typically it's "You're number three following the two Cessnas". They seem to almost fly out of sight on downwind before turning base. Periodically, I still practice power-off approaches at a nearby field that has minimal traffic.
 

Bob Turner

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My father lived in Flowing Wells. Visited a lot in the very early 1970s. Neighbors called the airport when I would do slips - reporting a “crash.”