Saturday, July 10, 2010

Jacobson's Ladder

Most new instructors start out by teaching student pilots almost exclusively. After several months of watching, correcting, and saving their students (and themselves) from various landing catastrophes, they may begin to wonder "Do I still know how to perform a respectable landing?" Now a seasoned instructor, I still find it challenging to impart the important skills involved in getting a plane safely back on terra firma. There's nothing like teaching a student pilot how to land an aircraft for putting a flight instructor back in touch with beginner's mind.

A crucial trait for flight instructors is being open to new ideas. Truth be told, every week we instructors stand to learn (or re-learn) something important from a pilot that we're supposed to be educating. Then there's the other end of the spectrum: Instructors who think they have seen it all and know it all. After giving hundreds or thousands of hours of dual instruction, falling into a rut is all too easy. And so I found myself feeling a bit skeptical when a student who had been wrestling with inconsistent landing performance introduced me to something he had found on the Internet. It's known as the Jacobson Flare.

Before going any further, let's get this out of the way: The Jacobson Flare is not a parlor trick. It doesn't involve a deck of cards or a pact with the devil. Jacobson uses the pilot's Eye-to-Wheel Height (or EWH, based on the aircraft type), the pilot's offset from the main landing gear (also based on aircraft type), the airplane's approach angle (usually 3 or 4 degrees), and simple geometry to determine visual references on the runway surface where the pilot can aim and begin the landing flare. One of Jacobson's documents even has an appendix that lists the calculations for several transport category aircraft as well as several GA aircraft.

I followed the link my student sent me, downloaded, and then read the various documents. And I watched the two videos, one of which clearly demonstrates the technique in a C172. I was intrigued, but still skeptical.



It helps to understand the dimensions of runway markings when choosing an aiming point and a suitable cutoff point (where the landing flare will commence, based on your aircraft type and descent angle). You can find some important details in AC 150-5340-1J: Standards for Airport Markings.  At most airports you will encounter one or more of three basic types of runways: Precision, non-precision, and visual. The markings and dimensions for each are shown below. Remember that there are airports out there with non-standard runway markings, so be careful about assuming the length of the centerline stripes, how tall the runway number are, or the length of the gaps between the centerline stripes.




The day after reading Jacobson's material, I had the opportunity to try out the technique with a fellow instructor who was doing some instrument currency work. On her first landing, she mentioned she had to suppress some of her normal landing instincts, but the landing was very good (7 out of 10, I'd say). We both felt skeptical until her second landing, which I would describe as a 10. Okay, interesting, but still too small a sample from which to draw any meaningful conclusions.

The second day I flew with an instrument pilot for an aircraft check-out flight. I explained the landing technique and he was game. His first landing was a 7 - not bad considering it involved an 8 knot tailwind component. His next two landings were a 9 and a 10 respectively. This was interesting considering he hadn't flown that particular aircraft type in quite a while.

The third day I flew with a student pilot and saw equally pleasing and consistent results. His normal, short field landings, even a power-off approach, were all 9s. He was excited and so was I. We switched to crosswind landings, his concentration wavered a bit, but the next two landings were a 6 and 7 (not bad considering a 15 knot direct crosswind). I mentioned that he had flared too high on one landing and he immediately recognized the problem and agreed. From an instructional standpoint, this is significant: Instead of a vague sort of Goldilocks process - "That flare was too low, that flare was too high, Oh! That flare was just right, do that again!" - Jacobson provides objective visual references on which the pilot can concentrate.

The past week has provided the most fun I've had watching people do landings in a long, long time. Yesterday, it was my turn to do a couple of landings - one normal, one short field. I don't mean to brag, but my first landing using Jacobson's Flare was an 8. My second landing was a short field effort. I not only touched down on the selected target, it was a very soft touchdown at minimum speed - a definite 10.

It's my considered opinion that pilots who learn to apply Jacobson's techniques can make consistently good landings, provided they know how to configure their aircraft and fly a stable approach at the appropriate airspeed. Pilots still have to develop and maintain a feel for their aircraft and learn how to handle crosswinds and gusty conditions, but Jacobson's procedure is very useful. And when you haven't flown in several weeks or it's your first landing in a new-to-you aircraft type, Jacobson's approach gives you something on which to hang your hat.

From a teaching perspective, there seem to be three main advantages to Jacobson's technique: First, it gives the pilot objective visual criteria for when to begin the landing flare, tailored to their type of airplane. Second, it provides visual cues to concentrate on throughout the flare. Every experienced pilot knows that landing performance improves when they are concentrating or, in the case of challenging conditions, they are forced to concentrate. Last, but not least, applying this technique will undoubtedly save the student time and money (not to mention the wear and tear on training aircraft).

Of course there are exceptions and limitations. It would be foolish to try to apply this approach to every possible landing situation. Simply watching a video will not teach you how to fly and land an airplane. Jacobson's material doesn't contain data for many newer GA aircraft, though I'm putting together a spreadsheet of measurements for some of the aircraft I fly. There are runways and landings surfaces that have no markings, including grass, dirt, and gravel strips not to mention bodies of water used by seaplanes. Anytime you try a new technique, it's wise to consider having an instructor along.

Even with these caveats, I'm excited to have a cool, new tool in my teaching toolbox. I can't shake this feeling of a kid in a candy store. As the instructor I flew with today said after her last landing, "Thanks, Jacobson!"

14 comments:

Flyin Dutchman said...

Very interesting, stuff...gonna have to give it a go. What about gravel runways which are about 50 percent of my day ? :)

Cheers,

FD

Steve said...

Interesting post, as Keith said. I'll definitely have to read into this a bit more!

Julien said...

I had heard about it but always thought the Jacobson Flare would only apply to airliners with a high EWH, not to GA aircraft. I stand corrected.

My big breakthrough moment personally was when I took my eyes off the runway in front of me and started looking at the horizon to judge when to start flaring.

Sarah said...

I'm having a little trouble making a practical method out of the linked material.

It seems to me to be just another expression of "that looks about right". Clearer, in that the cut-off point defining when to start the flare is defined. But once the flare is started, and the new aim point is flown up the runway, I don't see a difference.

I'll look at the zip'd movies when I get home. Maybe there are more details there.

Brent said...

Reminds me a little of what is taught in landing gliders.

John Ewing said...

Sarah,

First, what type of airplane are you flying?

If you've downloaded the package of files, go to the document "The Jacobson Flare Paper - Where to Flare" and look for appendix E on page 15. Find your aircraft in column 1, the look for the Δ x value in column 6. The cutoff point for your aircraft is distance shown in column 6 - this is the distance before the aiming point at which you'd start the flare.

Make sense?

Sarah said...

Gliders, BE23, C172, PA28... the singles all have about the same magic number - 300' from the threshold to aim, 200' from the threshold for the cut-off point.

I can understand the appeal of this method for varied, larger & faster aircraft.

I'll give it a try. It may be very helpful for my frustratingly inconsistent night landings.

John Ewing said...

Sarah,

My experience to date is that it is much more helpful to think of the aiming point and the cutoff point only. The distance from the threshold for the nominated aiming point obviously needs to be considered carefully based on the runway length, obstructions, chosen descent gradient, and aircraft performance.

toddgrx said...

I'm going to learn and have CFI David work with me. I like the part about "saving wear and tear on the training aircraft"... Tulip could use a day off of smash 'n go's.

Terence Wilson said...

Thanks for the article John. Great stuff!

Rajpinderjit said...

I was having a little trouble understanding the final parts of the Jacobson flare. I would greatly appreciate if you can help with the last few points of your lesson. So after you have passed the cut off point, (approx 90 feet before your aim point for C172), you begin to flare, and then it looks like you're focusing on aim point 2. But now what are you doing in regards to aim point 2 during your flare. Are you trying to slowly bring the nose to touch aim point 2 line of sight? Are you trying to keep the same distance between the nose and the aim point 2? Does your aircraft nose ever go above aim point 2? It also looks like the aim point 2 was closer first & than it moved farther, which you explain that fly your eyes to aim point 2 in 3 to 4 seconds. Can you please elaborate.

John Ewing said...

Rajpinderjit,

I recommend you follow the link to Jacobson's site, download his materials and read "The Jacobson Flare Paper - Where to Flare.pdf".

Quoting from that paper:

"1. Hold an accurate eye path to the nominated aim point, utilising ILS, VASIS, or PAPI if available, in the ‘slot’, within nominated limits.

"2. When the aircraft glare-shield superimposes the pre-determined flare cut-off point, start the flare, reducing thrust as discussed above.

"NOTE: Do not try to watch the cut-off point pass under the nose. Maintain most attention towards the aim point and note the visual flare fix occur in the lower peripheral field. This greatly reduces the possibility of a premature touch down before the flare is completed.

"3. Fly the eyes progressively up the runway over 3-4 seconds until the new aim point is moving neither up nor down in the visual field, check that thrust has been reduced to a minimum and continue to ‘fly the eyes’ towards this point until touch-down."

With some students and some pilots, I've found it helpful to to place a mark on the windshield with a grease pencil once the student has begun descending toward the aiming point.

As you begin the flare, you slowly pull the yoke/stick back to gradually move that mark up toward the end of the runway. How far up you move the aiming mark depends on the aircraft you are flying. In Cessna singles, I bring the point up fairly high. In a tailwheel aircraft doing a three-point landing, just bring the point up to where the three-point attitude is attained. In a heavier single or twin, the point is not going to move up quite as high.

Hope that helps ...

Rajpinderjit said...

Thanks. I've actually downloaded all the material. But its the line that says fly the eyes to the aim point 2 in 3 to 4 seconds, was a little confusing. Am I moving (pitching) the airplane, which in return moves my eyes up? And again, once I have the aim point 2 in sight, for a Cessna 172, should I be trying to bring the nose closer to it as much as I can or keep a small distance between it and the nose? Thanks

John Ewing said...

Rajpinderjit,

In general, after you pass the cutoff you are gradually pitching the aircraft up, moving your aiming point from the spot on the runway to the end of the runway, and then perhaps a bit higher. How much you pitch up depends on the aircraft, whether it is a tricycle gear or tailwheel, the flap configuration, the aircraft power- and wing-loading, etc.

There are limits to how much theoretical knowledge can illuminate the psycho-motor domain (i.e. physical skills). I obviously can teach you with words alone and at some point you have to apply his in a real aircraft.