In response to my explanation of pitch deceleration on short final to cause sink and thereby activate the glide control of a now dynamic throttle, a pilot asked if this was like autothrottle. Not knowing I could not say. From the airline passenger seat I have heard either manual or autothrottle changes on approaches. I assume, however, that autothrottle is only used on Category III approaches. Someone enlighten us.

Dynamic throttle is an essential part of any power/pitch approach to get the airplane down slowly and softly in the beginning of the landing zone. Should we call our manual throttle pilot controlled autothrottle? I never accepted the school solution of setting RPM and then ignoring our best glide angle and rate of descent control. Where does the need for stabilized RPM come from? Doesn't that force the pilot to control both glide angle and airspeed with elevator? This need for stabilized RPM takes away the much more efficient glide angle control, the throttle, and forces the runway consuming round out and hold off. I assumed all this was necessary so that pilots would be ready for large airplanes and much faster approach airspeed and round out and hold off. And then a pilot asked me if using the throttle dynamically, as I teach, was like autothrottle. What did I miss here?

I mostly liked it on STAR descents, I’ll dial up my target speed and cross X point at X feet and it’ll do the math on decent angle and adjust the throttle to meet my speed selection.

On final in a smaller kerosine burner, it just holds airspeed, the FMS will have the airspeeds, lots of times the monkey just changes flaps and it re adjusts target speed for flap selection and moves the throttle. Mostly found in FADEC planes, since once fadec a auto throttle isn’t that much of a add. The new Pilatus can even do a visual approach, it’ll take you over the fence in final at speed, my only draw back is it’s the pre programmed speed vs flying short final on AOA. Still cool, but not anything I couldn’t do without.


Personally when it comes to big airplane things in more normal sized stuff, I’d take anti skid before auto throttle any day of the week.

So is the computer set up to adjust speed reductions with dynamic throttle and adjust glideslope with pitch changes like they teach manual instrument approach now? Is airspeed reduced during the approach or set to 1.3 Vso to the fence like the school solution for round out and hold off. From my point of view in the back, the airliner seems to decelerate to very near touchdown as I do in a 172. I don't have a problem with the backwards power/pitch of the modern instrument approach where power is speed and pitch is glideslope when airspeed is fast all the way down to make that possible except that that eats up more runway. I do have a problem with power controlling airspeed and pitch controlling glide angle and rate of descent in our small airplanes where we want to be able to get into the beginning of the landing zone by decelerating on short final. How does muscle memory handle the necessary change for STOL?

Anyway, as I observe automated robotic devises, I notice that the servos are quite active continuously for dynamic proactive stability. How would a robot stand still (hover)? How would a robot move the rudder to maintain a target or would it bring the ailerons into play on short final to make coordinated turn corrections to heading? I think it would be a tail wagger like me rather than a wing wagger. After all, that is how it stands up. How would a robot balance a broom on its hand? Ailerons, with adverse yaw, don't take kindly to the dynamic proactive movement necessary for stability in many mechanical things. The rudder, or any centrally mounted control like elevator or power, takes more kindly to dynamic proactive movement. Dynamic neutral stability lives with the ailerons by lowering the nose in turns the same as to correct for a pitch up. Trim is limited, except in the Max 8 fiasco, to prevent override of dynamic neutral stability.

I'm not a mathematician, scientist, or engineer. I'm just a lowly pilot who goes totally by what he experiences in airplanes and helicopters and other machines. Correct me where wrong on the physics or robotics.

At least with the ones I have flown, the AP will fly the same profile with AT disabled

Ships have gotten big enough to span multiple waves now, which provides stability. At least less pitching up and down, I would think. Airplanes are not that big. I don't see the fixed throttle approach as being stabilized, but have no problem with it far out. Getting close in where airspeed reduction promotes safety as in hitting the runway and other things less hard would require dynamic throttle I would think. At least I don't want to depend on a long, long runway bailing me out. Airplanes can handle speed quite well when airborne, even in low ground effect. At some point, however, we have to decelerate well below Vso to get the machine onto the surface without some damage. It certainly should still be flying at Vso in low ground effect (hold off). The only way to get safe sink and balloon control is with throttle and not elevator. In an unstable environment sink and balloon control has been necessary in my experience and elevator does not safely control that when slow. In fact, at altitude and cruise airspeed, elevator is a very effective control to work with up and down drafts. By pitching up in updrafts and down in downdrafts, we can increase ground speed and altitude over time. This on course thermalling technique doesn't work well, however, while getting "all slowed up and ready to squat."

Just like a smaller aircraft on final, once stabilized, decrease power- your rate of decent will increase. Reduce pitch= airspeed increases. The way I teach, use that power as an elevator control, how fast your rate will be. Use that pitch how fast you want to fly.

Now my long-wind explanation of auto trim and auto throttle. Yes, I used to work for a major OEM in Seattle. Skip, if boring.

Large jets with AT-Authothrottle, can be flown ON to a landing but most airline policies don't allow - UNLESS your flying fly-by-wire jet such as 777 or 787. This is due to auto trim fixing all kinds of issues mainly PIO- Pilot (or Pitch) Induced Oscillation is the issue, if power is surged, then the pilot is required to adjust pitch down, then then reverse, pitch up. All of this leads to power in and out, and pitch up and down which can lead to a hard landing or tail strike. Adjust all this by going AT OFF, adjust power by hand. Again, Boeing doesn't limit AT off by landing but their Flight Crew Training Manual recommends off for this PIO. No such problems on 777/787/797. For 737, 757, 767, 747 Simply, autopilot off, auto throttle off. Airbus 320,330, 340, 350 all have FBW, thus full time auto trim and can leave AT ON for a manual landing.

If the airplane is to autoland, then AT remains ON because auto trim stays on to touchdown or rollout.

In my work jet I’ll leave the auto throttle on typically until the radar altimeter calls 100 feet, I’ve never really seen a problem with the autopilot disconnected with the autothrottle on.
My typical day at work I’ll disconnect the autopilot around 500 and throttles at 100. Yep I’m that lazy, but we’re also flying a 15 hour leg, and I’m tired.
In the Cub, a well executed approach and landing is one where I don’t touch the throttle after I turn downwind until I need power to taxi.

I see a nice but long hold off and soft field type touchdown with a little power, Amodel. Very good. What about gusty balloon and sink? With a little power and a light Cub, I could see you riding that out with your some power. Somewhat uncontrolled, however, as the elevator will not be happy doing both airspeed control and rate of descent and glide angle control. Set up perfectly from downwind would assume no large variables, would it not? I do understand that is the more common approach and school solution. I found it too limiting, however.

On biannuals, I tried to teach a little power/pitch but accepted that most would round out and hold off. I did insist, however, that dynamic throttle and not elevator be used to correct for the fall following the balloon that was common from being way too fast at round out. And in gusty air, I insisted on dynamic throttle to mitigate both sink and balloon. Wolfgang taught the spot landing managing the apparent rate of closure with elevator only because Cubs and most trainers had the Stromberg carburetor and as you know excess airspeed is hard to get in the small Continental engine Cubs. I just modified my dynamic throttle movement a bit and lived with the engine gasp from flooding the carb. I never had one completely quit.

I adjust my pattern and speed as needed. It’s something I don’t really think about very often, I don’t really even think about it unless I’m trying to teach it.
On a gusty nasty day I’ll leave half flaps and about 60ish on base and maybe 55 on short final. It leaves just a little more inertia to play with, and expect a little more firm landing. My patterns are dynamic, and change as the conditions change in how I fly them. It’s just inertia management.
As far as using the throttle use it if you need it….it’s always there. I just look at a perfectly executed pattern, approach, and power off wheel landing as 400 level stuff. If you balloon in the flare, we’ll then power is necessary and it can happen to anyone.
I wouldn’t expect a student or low time pilot to be able to perfectly execute the maneuver. And power off wheel landings, they are a thing of beauty when properly executed. Just enough flare to dissipate the extra inertia and a perfect wheel landing with no float makes me smile.

Definitely a worthwhile exercise and with an airplane that is really trying to work with you. I tried some of that putting the forty hours on a Corben Baby Ace for the cabinet maker who built it, but I didn't get real good. My instructor was hogging half the time in that single seat.