FAQ #6 Update: Landing by night – just as by day – the Jacobson Flare

FAQ #6 Update: Landing by night – just as by day – the Jacobson Flare

A recent question became a timely reminder that an expanded explanation on how to adapt the Jacobson Flare principles to night landings had been neglected, for too long. So, for current exponents of the JF, here is a suggestion that can turn your night landings into the same, exacting standards that you are now achieving, by day. It updates the information, previously found in FAQ #6, at https://www.jacobsonflare.com/our-most-frequently-asked-landing-questions/

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Disclaimer:

This is a technical dissertation, intend primarily for experienced pilots and to provide an interim supplement to the Jacobson Flare App. Less-experienced pilots are advised to treat the information contained herein, as information, only.

Please, do NOT attempt to apply the information, contained herein, if you are a new- or yet-to-be-user of the Jacobson Flare.

It’s NEVER a good idea to do anything in an airplane, for the very first time! By this we mean, do it with someone, preferably a flight instructor, who has done it before. Your safety is paramount. So, become proficient at using the Jacobson Flare by day, before attempting to apply it at night.

This information is directed specifically to pilots of 4-6 place single- and twin-engine-airplanes, below 5700Kg MTOW. Pilots of larger airplanes should be able to apply the principles to their current airplane, although the aircraft landing lights generally illuminate the runway fixed distance markings, which identify the correct visual aim point 1 for the airplane type. Alternatively. please feel welcome to contact info@jacobsonflare.com for further information.

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Early in the research and development of the Jacobson Flare, around 1985-87, I was a civilian flight instructor at the RAAF Point Cook Flying Club. I am not ex RAAF, myself, but was in the ‘right place / right time’, from 1983-89), in a more-or-less voluntary capacity.

I was able to flight-test and prove, in C150, PA-28 and PA-38 aircraft, the following technique on Runway 17 at YMPC – a classic  ‘black-hole’ runway, at night, located SW of Melbourne. Headed away from the lights of Melbourne city, the immense Port Phillip Bay is the black backdrop and, depending on the prevailing conditions. it can be difficult to discern the horizon. The lights of the Melbourne SE shoreline suburbs are not much help, either, late on final approach to land on 17.

There is no T-VASIS or PAPI – or ILS glideslope to hang your hat on, so it’s a ‘Mk 1 eyeball’ approach, but this solution worked perfectly at YMPC and can be adapted easily to the night situation. Let’s take a look at the following standard 5 JF questions and re-examine what we use by day and what we can adapt for night landings. Again, a reminder that this discussion is directed specifically to pilots of 4-6 place single- and twin-engine-airplanes, below 5700Kg MTOW, who are familiar and proficient in applying The Jacobson Flare to their operations by day.

NOTE: The ft / m conversions have been rounded, for convenience. It makes no practical difference to the landing outcome.

  1. Where to aim?

The JF-recommended visual aim point, at 300ft / 90m from the threshold – for 4-6 place single- and twin-engine-airplanes, below 5700Kg MTOW – is still ‘King’, to assure 10ft threshold clearance of the MLG. By day it’s the ’top’ of the first centre line mark, past the runway numbers. So it is, normally, by night. Now, the runway edge lighting is a great reference, as you can use the normal (90º) axes across the parallel pairs of edge lights, as longitudinal references for both the aim point 1 and the flare point.

My recollection is that at YMPC, they were at a standard 60m spacing, but this vital information is not published, currently, in Air Services Australia’s ERSA. However, like many things in aviation, they are not as standard as they should be: For example, Australia’s busiest GA training aerodromes: Brisbane YBAF, Sydney YSBK, Melbourne and YMML, Perth YPJT have their runway edge lighting spaced at 90m intervals. Adelaide’s YPPF is not specified.

Fortunately, these variations are covered by the tolerance of the Jacobson Flare’s unique longitudinal flare point principle.

Accepting but ignoring the standard runway threshold green lights:

  • At 200ft / 60m standard spacing, the 300ft / 90m aim point 1 would lie mid-way between the axes of the first and second pairs of edge lights; the flare cut-off point is 100ft / 30m back from aim point 1, at 200ft / 60m, exactly on the axis of the first row. See the 60m spacing illustration directly below:

  • At 300ft / 90m spacing, aim point 1 would fall exactly on the axis across the first pair of edge lights, at 300ft / 90m and the flare cut-off point would lie 100ft / 30m back from there, at 200ft / 60m

However, having different aim- and flare-point indicators for the same actual aim and flare point locations is less than ideal; and  you may or may not have the luxury of being able to check the light spacing before you land somewhere – and the info may not be accurate, anyway. You’d be amazed at the quality of these specs, sometimes.

So, to keep things simple, consistent and conservative, let’s establish a single, consistent assumption for all aerodromes that you are likely to use at night and:

Assuming the conservative figure of 200ft / 60m and set the NIGHT aim point 1 mid-way between the axes of the first and second pairs of edge lights, exactly as it is, by day, at 300ft / 90m;

Now, if the spacing was actually 300ft / 90m – and we aimed at the same NIGHT aim point 1, mid-way between the axes of the first and second pairs of edge lights then the ACTUAL aim point 1 location would be located at 450ft / 135m, somewhat deeper.

Given that the test pilot-certified landing distance is factored by 67% for other pilots, again no practical issue, as long as the App is flown accurately, within +5/-0kts. See the 90m spacing illustration directly below:

 

  1. How to aim?

No change is needed. Fly the same aim point 1 / glare shield relationship as by day – controlled with the elevators and airspeed controlled with power/thrust – to achieve the essential stable approach path.

Aim point 1, as discussed above, is the mid-point of the imagined axis, longitudinally mid-way between the axes of the first and second pairs of edge lights; in other words, the centre of the black space between the first 4 edge lights.

 

  1. When to flare?

This where the 1:20 advantage of a longitudinal flare point assists, greatly. We already know that the flare cut-off point is 100ft / 30m back from aim point 1.

For 200ft / 60m spacing, aim point 1, mid-way between the axes of the first and second pairs of edge lights, is perfectly located at 300ft / 90m, so the flare point will be located on the axis through the first pair, at 200ft / 60m, exactly as by day.

As stated above, if the spacing was 300ft / 90m – and we aimed at the same NIGHT aim point 1, mid-way between the axes of the first and second pairs of edge lights then the ACTUAL aim point 1 location would be located at 450ft / 135m, somewhat deeper. The correct flare cut-off point for that aim point location would lie 100ft / 30m back from there, at 350ft / 105m.

However, to be consistent with the 200ft / 60m case, we might wish to use the same flare point indicator, namely the axis of the first pair of edge lighting, at 300ft / 90m. This would create an actual  flare cut-off distance of 150ft/45m: an error of 50ft / 15m.

Yes, it’s a little earlier – and correspondingly higher, BUT:

The longitudinal error is 50ft / 15m: Applying the 1:20 advantage, (dividing by 20) indicates a diminished vertical error of just 2.5ft / 0.75m. This is well within the tolerance of any landing, flared using the conventional educated guess of height.

Speaking of flare point tolerance, it has been found useful to regard the flare point much like a CG, lying within an acceptable range between a forward and an aft limit. This an example of that principle. Now, at a 3-4º approach path angle and flaring over the usual 4-seconds to a new aim point 2, probably at least 2000ft / 600m away, or even further, it makes little difference whether you flare at the aft limit, the forward limit, or anywhere in-between: it is such a small angle

The point is you can use the one aim point 1 and the one flare point for runway edge lighting spacing of 60-90m spacing and the 4-second flare will smooth out the differences, due to the 1:20 tolerance of using a longitudinal flare cue.

See the 90m spacing illustration, above:

Finally, use EVERY cue at your disposal, including your experienced assessment of vertical flare height, too. Triangles still have three sides! We might as well use all of them.

Airline fleets and other advanced types offer the added advantage of computer-generated call-outs of ‘50-40-30-20-10‘ ft radio altitude (‘radalt‘), from the ground proximity warning systems (GPWS). (However, these are still subject to certain limitations, such as radio interference and the mathematical fact that, on the standard 3º flight path angle, every +/- 1ft vertical error compounds as a longitudinal error of +/- 20ft respectively, along the runway.)

 

  1. How much to flare?

Again as by day, transition to aim point 2, at the end of the runway lights! For a runway of uniform slope – not necessarily level –  this is the same as used by day: the upwind threshold.

 

  1. How fast to flare?

The usual Jacobson Flare 4-second technique, or maybe stop the flare at 3-3.5 seconds, if the runway has a lot of water on it, to reduce the risk of aquaplaning.

(In a jet, aiming at aim point 2, after completing the flare, can provide too good a landing! The main wheels don’t penetrate the water layer and make ground contact, so apart from the risk of aquaplaning, the main wheels don’t spin up to about 700rpm and, in some airplane types, the pre-armed auto brakes and auto-spoilers don’t actuate – they actually get ‘confused’.)

So, there you go. It’s a bit to digest:  Try drawing it out on some paper, to scale for your airplane; think it through; sit in a chair and visualise the whole thing. And try it, first time, with someone else, preferably a flight instructor, with you, or better still, have a play in a simulator. It may be very beneficial, to prove it to yourself.

Finally, use all available cues available, including the landing light-illumination of the centreline and fixed distance runway markings and your accumulated experience, (together with the GPWS radiant callouts in larger aircraft), in assessing your height above the runway.

Of the three components to any landing:

1. The initial pilot’s eye path to aim point 1;

2. The commencement point of the flare; and

3. The flare, itself, through to the second aim point, usually at the far, upwind threshold:

The first is the most important; second most is the third and the least important is the flare initiation point, so long it within reasonable limits for the airplane type, as discussed above.

Finally, to reiterate, the one aim point 1 – at 1.5 rows of edge lights – and the one flare point – at the first row of edge lights – may be applied for runway edge lighting spacing of 60-90m spacing and the 4-second flare will smooth out the differences.

See the generic spacing illustration for 60-90m edge lighting spacing, below:

 

Happy Landings

 

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David Jacobson