What is a Trimmable Horizontal Stabilizer(THS)? Why THS is Required? How THS operates? Aircraft Trim

[@Hopeless_and_Forlorn]

Nice explanation. As background, the trimmable horizontal stabilizer was developed out of necessity after high-speed aircraft in WWII developed a troubling tendency while diving to go nose-down. After it was realized that airflow over the control surfaces was going transonic and causing large changes in trim, it became obvious that it would be necessary to use the larger area of the stabilizer to aid the elevator system in maintaining control. One of the first aircraft to use a "flying tail'" as it was once known, was the Bell X-1 rocket plane which Chuck Yeager used to break the sound barrier in 1947. To understand the twin roles played by the elevators and horizontal stabilizer, think of this: the elevators are quick-moving, the stabilizer is relatively slow moving. To adjust pitch attitude short term, such as recovering from a "bump" of air turbulence, use the elevator. To maintain a constant attitude, and therefore altitude, use stabilizer trim.

[@JxJAVIATION]

Thank you so much for sharing this knowledge! Very Useful!

[@brav0wing]

It was with this Trim Stabiliser that MCAS played with during the crashes of Lion Air 610 and Ethiopian Airlines Flight 302. When MCAS detected a angle of attack that would have resulted in a stall it kicked in moving the Horizontal Stabiliser to increase the angle of attack by pushing the nose down. The pilots of Lion Air trimmed the nose up over 30 times resulting in a up, down movement of the aircraft before it crashed into the Java Sea. They basically fought the MCAS.

[@JxJAVIATION]

Yes! Thank You for sharing this information! Very useful to viewers and learners

[@vireng.9418]

At first I got confused with MCAS and THS but now it's cleared!! Thanks😄

[@mrbilly0036]

Wow

[@mugundhann5905]

Very nice explanation bro

[@JxJAVIATION]

Thank you. Check out my other videos as well!

[@mohdfaisal3418]

Good explanation and make the concepts clear👍👍

[@JxJAVIATION]

Thank you, Check out my other videos as well!

[@danielpeter2802]

Great video

[@JxJAVIATION]

Thank you!

[@williamwidjaja850]

Thank you, i understand now a movable horizontal stabilizer

[@JxJAVIATION]

You are Welcome!

[@flywithkhalil4359]

Great Video mate! Now I understand how the Boeing 737 MAX accidents took place, primarily how much of an effect MCAS had on the Horizontal Stabilizer.

[@JxJAVIATION]

Thank you so much. Do check out my other videos as well!

[@수페르피포]

Thank you for the video

[@JxJAVIATION]

You're welcome!

[@zackl7673]

Very interesting. Thank you for the video

[@JxJAVIATION]

Glad you liked it! Check out some of my other videos as well! :)

[@Mouka97]

I think the trim tab is made to maintain a certain speed IAS, not Altitude nor rate of Climb/descent.

[@JxJAVIATION]

I would say it works both ways depending on the requirement.

[@atakancalik8306]

Great vid

[@JxJAVIATION]

Thank you!

[@kevindunlap5525]

A trimmable horizontal stabilizer is a horizontal stabilizer that can be trimmed.

[@JxJAVIATION]

True. And video shows why it is required...

[@kevindunlap5525]

@@JxJAVIATION Dang, I didn't see that part. I'm going to guess that maybe since it's on the plane it's required?

[@hilmarh.werner8882]

please, how does an aircraft react to the loss of weight due to fuel consumption? I assume that, in the first place, the "angle of incidence" is chosen so that the airplane, with half of its fuel weight gone, flies at an optimal condition, i.e. with an angle of incidence = 0 (in mid-flight), using just the airfoils lift due to its profile and its "angle of attack", without using flaps, slats or any other control surface. but what does it do in the non-optimal states of a) full fuel weight and b) fuel weight down to reserve? in a) it may fly at an increased pitch angle to the flight path or it may use slats and/or flaps (?) and in b) it may compensate for a surplus of lift (with speed constant) by using the flaps in an upward bent position (?) or by flying with a negative pitch angle (or reducing speed)... what's the case in reality please? thank you!

[@Primus54]

As the aircraft sheds weight from fuel burn, it will naturally gain altitude if either the power remains constant or the AoA is unchanged. Modern aircraft have a small switch on the control yoke pilots can activate with their thumb to change the horizontal stabilizer trim instead of using the trim wheel shown in this video. If you watch some of the videos on KZbin of actual cockpit operations, you can notice the trim wheel frequently moving in all phases of flight, mostly commanded by the auto pilot.

[@kevinthomas5364]

As mentioned by Primus, I agree that altitude would increase with fuel burnup (assuming manual control with no pilot input). Fuel tank levels are managed however to occur equally across all tanks and would not affect the center of gravity therefore attitude should not be affected by fuel burnup. BTW - I'm not a pilot but I have a fairly good understanding of "fluid flow" and it's interaction on or within surfaces (and yes, air is a fluid).

[@doveliuqf7895]

good video to point ,thank you

[@JxJAVIATION]

You're welcome:)

[@cornucopiahouse4204]

Isn’t all horizontal stabilizer trimmable?

[@JxJAVIATION]

Most of aircraft have trimmable stabilizer and some don't!

[@cornucopiahouse4204]

@@JxJAVIATION What are some airplanes that don’t have elevator trim?

[@JxJAVIATION]

@@cornucopiahouse4204 Aircraft having T Tail or V Tail Configuration

[@cornucopiahouse4204]

@@JxJAVIATION Must be hard to fly those kinds of aircraft...

[@joex8279]

​@@JxJAVIATION Just 2 items. 1: Trimmable Horizontal Stabilizer or THS, is an Airbus term. Most other manufacturers just can it the horizontal stabilizer, trimable or not. 2: Concerning which aicraft have trimmable stabilizers and which don't, it is actually aircraft size derermines it, not the type of tail dedign. The MD-80/DC-9 being a perfect example

[@NisarAhmad-jr6ol]

The term is altitude not attitude.

[@JxJAVIATION]

The THS maintains a particular attitude: so it can be used for level flight, constant rate of climb or constant rate of descent.

[@NisarAhmad-jr6ol]

@@JxJAVIATION I was bringing your attention to your spelling mistake. The height is termed as ALTITUDE not ATTITUDE.

[@lospazio]

@@NisarAhmad-jr6ol "Altitude" and "attitude" are two completely different things. The video refers correctly to the attitude of an aircraft. The altitude has nothing to do with this matter.

[@il400]

settle down there Dunning Kruger

[@NisarAhmad-jr6ol]

@@il400 Shame on you for your unwarranted response rather than admitting to your spelling error.

[@SherriP]

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[@Hopeless_and_Forlorn]

I'm sorry, but this post is about technology, not insanity. The rubber room is next door. And, next time you find yourself on a burning, falling airplane, remember--nothing fails like prayer.

[@mayaq8324]

Another Worthless video on the subject

[@JxJAVIATION]

please elaborate!

[@alexandergordon7203]

Trim issues aren't confined to Boeing. Here's an interesting example involving a A300: aviation-safety.net/database/record.php?id=19940426-0

[@JxJAVIATION]

That's good information. Even the newer Airbus have some minor trim issues.