Two pilots in a cow suit: Mastering the Approach_JF-ai podcast

We revisit this earlier post and introduce a couple of friendly AI ‘aces’, whom we’ve nicknamed ‘Jay Bird’ Jaime & ‘Fearless’ Frank.

Simply select the Play button below, for a 5-minute JF–ai podcast summary of this post

Of course, if you’d like some further elaboration, just scroll down.

 

Two pilots dressed for a fancy-dress party, in a cow-suit .. or .. What controls what, on final?

Do you know why some pilots still try to fly a POWERED final approach using the SECONDARY effects of the PRIMARY flight controls?

Neither do we!

We shall discuss glide approaches, later in this article. But arguing about what controls what, on a final approach – when variable power or thrust is available – has occupied far too much time and confused far too many pilots, for over 100 years. It is vital to the understanding of HOW to aim the approach, accurately, yet the argument still rages. It shouldn’t.

Let me conceive a comical image: Imagine how ridiculous-looking, ungainly and haphazard would be the sight of two pilots heading out to a fancy-dress party, dressed in a COW SUIT.

The guy in the front would, presumably, be responsible for finding their way to the venue and steering the ‘beast’, while the poor individual providing the hindquarters would essentially maintain a stooped-over profile and act as the limiting factor on their speed, neither pushing too hard, nor allowing the front half to drag him/her along, too fast.

Now, please hold these thoughts for a minute or two.

On a normal, powered, manually-flown approach, the pilot has one hand holding the control column and the other hand on the throttle and, together with the brain of  the pilot, the complete approach is coordinated. But what controls the flight path along the extended runway centreline? And what controls the airspeed? Pilots have argued over this, for decades.

It is instructive, therefore, to consider how an ‘artificially-flown’ approach is constructed.
In an airliner, conducting an ‘auto-coupled instrument approach’, the autopilot and autothrottle systems perform the same functions, respectively, yet quite independently from each other, using only the primary effects of controls.

The autopilot controls the flight path along the electronic extended runway centreline path and the 3º glideslope, while the autothrottle maintains the selected approach airspeed.

Now, these two ‘black boxes’ under the cockpit floor are completely unaware of each other’s existence. It is the automated flight control system (AFCS) that coordinates their inputs (along with many others) to control both the approach path and airspeed and simulates the manually-flown approach with impeccable accuracy and stability.

Moreover, because the aircraft is not pitching up and down, the stability of this ‘PATH’ descent also facilitates the application of the unique Jacobson Flare visual fix. It is an accurate, far straighter flight path than the ‘conventional roller’ coaster path of varying amplitude and runway threshold crossing heights, resulting from pitching to maintain approach airspeed. A handy side-effect is enhanced passenger comfort, especially in large aircraft with inherently great inertia and a limited supply of  airsickness bags!

There are two occasions, however, when it is appropriate to control airspeed with the SECONDARY effects of the elevators:

On take-off and in the subsequent climb, for example, with take-off power or climb power set, the pilot must utilise the elevators to control the airspeed. There is no alternative.

The second occasion is on approach, IF the power output is constant (or failed, partially or completely). It is necessary, then, to control airspeed with the elevators (along with refining the approach path angle, through judicious tracking and deployment of landing flaps). This is generally a training manoeuvre, such as when practising a NON-NORMAL procedure, such as a forced landing. It is a compromise – inaccurate and results in an oscillating, inconsistent, ‘rollercoaster’ path.

Sailplanes (gliders) are normally flown this way; for without power, these aircraft are always descending through a parcel of air which, hopefully, is itself rising faster than the actual descent rate of the sailplane within it (that is, a thermal).

Using the secondary effects of the flight controls. ‘Elevators controlling airspeed’, with the nebulous concept of ‘power/thrust facilitating rate of descent is valid only when power/thrust is fixed (or lost, entirely) and is ineffective on heavier and/or faster airplanes. A roller coaster flight path is the inevitable result, leading to unstable approaches. This is one of several major reasons for inconsistent and poor-quality landings.

The costs are immense, in terms of time, cost, pilot stress and aircraft damage. Many instructors insist that airspeed is controlled with the elevators and the vertical rate of descent is controlled with power. This is misconceived. The use of an increase in power certainly does facilitate descent flight at a reduced path angle, for a given airspeed: However, it is the reduced path angle that reduces the rate of descent, not the power. This particular point has been long-lost in the translation, over the last 100 years.

The rate of descent on an approach is, simply, the result of two variables: the flight path angle and the aircraft’s ground speed.

Now, why would anyone want to apply the secondary effects of controls, rather than the primary effects, IF THEY DIDN’T HAVE TO, when flying the most precise manoeuvre that most pilots ever need to master? Not to mention making so many corrections of corrections. Absolutely NOTHING remains stable: Not the power setting, the elevator inputs, the path angle, airspeed, vertical speed or aircraft trim.

Another critical issue is to consider the two common errors that student pilots (and licensed ones also) who have been taught this inappropriate method, make frequently:
1. High and fast on final approach; and/or
2. Low and slow.

In each case. the initial response for a pilot trained to think that the elevators control airspeed, will COMPOUND both problems, because his or her priority will be airspeed, not flight path.

The pilot who is HIGH and FAST will pitch UP making things worse and the pilot who is LOW and SLOW will pitch DOWN -the LAST things the pilot should be doing to resolve each of these errors!

The next major issue is that the roller coaster flight path ensures that the threshold crossing height of the aircraft will be totally inconsistent, making landing judgment quite haphazard, with no guidance through the flare. Then, there is the significant issue of when to initiate the flare.

And because of the very ‘flat’ standard approach angle of 3 degrees, ALL vertical errors in height judgment compound 20-times, one way or the other, along the runway: Long if high, short if the guess is low, compared with the optimum flare height.

How can an instructor demonstrate the flare height as being ‘about here‘ or ‘about now’, when the picture is different, every single time?

As if all of that is not enough of a problem, the situation worsens at a most critical phase: the flare point. A pilot, incorrectly pitching the airplane with the elevators to control AIRSPEED, now needs to transfer the use the elevators to pitch the aircraft to control the FLIGHT PATH ANGLE, just as the flare is about to be initiated.

What a ridiculous moment to completely change the flight path control philosophy! It defies all logic.

Most approaches and landings are flown in powered airplanes, where the power output is variable and reliable: Therefore, the afore-mentioned PRIMARY effects of the controls should be applied: The constant approach path angle is maintained with the elevators, by aiming the pilot’s eyes at a suitable aim point and the throttle is utilised to vary the power, slightly, to maintain the selected approach airspeed (IAS) through each flap configuration and wind change.

There is, of course, no need to change your flight control philosophy, as the landing flare is initiated.

None of this is new to generations of military and airline pilots, but it often meets ignorant and stubborn resistance, by some misinformed general aviation (GA) flight instructors and, sadly, their unsuspecting students. Frequently, these same instructors contradict themselves, making no sense in teaching the speed technique to VFR students in light airplanes and then introducing the path descent when they progress to heavier and faster aircraft and IFR. After all, the airplane doesn’t know the difference between IFR and VFR! But it does know the difference between a powered and a glide approach and that is the arbiter.

OK, let’s return to where we started: Two pilots dressed for a fancy-dress party, in a cow-suit …

From the foregoing, it should become clear that flying a NORMAL, powered approach with a ‘SPEED’ descent, that is, with the secondary effect of the elevators controlling airspeed and power supposedly controlling the rate of descent/path angle, is just as silly as having the guy in the front of the cow-suit, who can see where to steer, worrying only about how fast they are going; and the guy down the back, who cannot see a damn thing, trying to find the party.

So, the comical and ridiculous cow-suit analogy is quite relevant.

There are many more advantages in flying an accurate ‘PATH’ descent: To learn more on this, please review FAQ #5, in https://www.jacobsonflare.com/our-most-frequently-asked-landing-questions/ . The Jacobson Flare App, of course,  expands at length, also, on this critical aspect.

 

Captain David M Jacobson

 

Wishing you many safe landings

 

Captain David M Jacobson FRAeS MAP

 

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