Trim Angle

[FLEX1978 373]

Going to be 14. 13 now (born november 2000)

Please ask the questions! I read the FBW system and the different angles (bank, fpa, pitch...) and read the THS. So the question came to me....

 

Just out of curiosity, what do you want to be when you are older?  A pilot? an engineer?  

[AF330 0]

An A330 pilot! My dream!

 

Could anyone give me an answer please?

 

Thanks

[LHookins 3,102]

Ok, so you're reading about a fly by wire system, probably on the A330.  They mention that the trim is limited to a 14 degree angle.  I don't know anything about that specific plane, but I understand the question. 

 

The elevator trim (the elevator makes the nose of the plane go up and down, the trim function of the elevator helps hold it in a specific position without the pilot holding a control) can be set to cause the nose of the plane to go up to a 14 degree "angle of attack", but no farther, as this would cause the plane to stall.  The angle of attack is the angle between the oncoming wind and the angle of the wing.  Somewhere above that 14 degree limit the wing will stall, which means it will no longer provide lift.  Normally you don't want to go there.

 

Does it say if the trim will be reduced automatically if it causes the angle of attack to be more than 14 degrees?

 

Hook

[Oracle427 45]

If youare very serious about this I very seriously recommend reading this

 

http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/pilot_handbook/

 

And for more details

 

http://www.av8n.com/how/

 

And relevant sections from this

 

https://www.faa.gov/air_traffic/publications/atpubs/aim/index.htm

 

This should give you a more than solid understanding of the basics.

 

I have been looking at all these parts and reluctant to answer the ones I understand simply because you are trying to do gymnastics before learning to crawl.

[AF330 0]

Thanks a lot,

The A330 is limited to 30 degrees pitch up and 17 degrees pitch down. So we can imagine that around 16-17 degrees of AoA, the plane has reached alpha max and it can't go further. The 14 degrees AoA (13.5 exactely) is equal to alpha protection. At that moment positive trim will stop.

 

1) What do you think?

2) Does anyone know how much 13,5 AoA is in pitch angle? It should turn around 25-26 degrees...

 

Thanks a lot!

[Oracle427 45]

Again you really need to read the basics because then you would never ask what the relationship between pitch angle and AoA is. It just doesn't make sense and it cannot be answered.

 

An aircraft can be at 0 pitch and cruising with a slight AoA. On the other hand it could be at 0 pitch with an AoA of 50+ degrees on one wing and greater than 90 on the other. This would be found in a spin.

 

The airplane could also be at a -90 pitch angle and at a 0 AoA in a vertical dive.

 

This is not meant to hurt your enthusiasm, that's great, but you should be able to go through the above material very quickly.

[FLEX1978 373]

 

 

1) What do you think?
2) Does anyone know how much 13,5 AoA is in pitch angle? It should turn around 25-26 degrees...

 

So you have no idea what trim is yet you understand Alpha Max & Alpha Prot??

 

This all sounds like you are cutting and pasting info of the web.. you have been given links and very good advice on getting to grips with the basics, I would suggest you take that advice.

 

If you do really want to study the A330 I would suggest reading FCOM VOL1, all your answers can be found in that document written by the people who designed the aircraft.

 

Here is a reference - FCOM 1.22.30  

 

Alpha FLOOR is activated through autothrust system when :
• Alpha is greater than a threshold depending on the aircraft configuration, the ground speed variation, and the difference between ground speed and air speed or,
• Sidestick deflection is above 14 deg and: 
— pitch altitude is greater than 25 deg, 
or AOA protection is active

[AF330 0]

"The airplane could also be at a -90 pitch angle and at a 0 AoA in a vertical dive."

 

Depends of RAF, I imagine...

Alpha prot comes at a certain angle, depending of many factors.

Yes, you can't predict it, sorry made a mistake. And yes Flex, pitch angle should be around 25 degrees, as you can't go how higer than 30 degrees for the A330- 33 degrees for the 320.

If you don't have AoA protection, you are not in normal law.

[LHookins 3,102]

 

 

Alpha FLOOR is activated through autothrust system when :
• Alpha is greater than a threshold depending on the aircraft configuration, the ground speed variation, and the difference between ground speed and air speed or,
• Sidestick deflection is above 14 deg and:
— pitch altitude is greater than 25 deg,
or AOA protection is active

 

Holy cow!  No wonder he's asking questions.

 

What does "ground speed variation" mean in that sentence?  What is "pitch altitude" and why is any altitude (other than Right Ascension which isn't really an altitude) measured in degrees?  If I were given the above to write a computer algorithm on, I'd be camped on someone's desk and not real gracious about it.  Find me a domain expert who can speak English, dammit!

 

Hook

[FLEX1978 373]

Holy cow!  No wonder he's asking questions.

 

What does "ground speed variation" mean in that sentence?  What is "pitch altitude" and why is any altitude (other than Right Ascension which isn't really an altitude) measured in degrees?  If I were given the above to write a computer algorithm on, I'd be camped on someone's desk and not real gracious about it.  Find me a domain expert who can speak English, dammit!

 

Hook

 

 

What does "ground speed variation" mean in that sentence?  What is "pitch altitude"

 

It should read 'Pitch Attitude'... Not sure what happened there..   Alpha floor is an Auto-thrust function,  it also has to make predictions using the FAC's based on the information it is fed. As explained above, variations in ground speed along with calculated differences between airspeed and ground speed is used to calculate when Alpha floor becomes active.

[WarpD 824]

Learn how a Cessna 172 flies... then ask about an Airbus.

 

You don't grasp the basics of flight which means at the end of the discussion, you know absolutely nothing.

[AF330 0]

"The airplane could also be at a -90 pitch angle and at a 0 AoA in a vertical dive."

 

Depends of RAF, I imagine...

Alpha prot comes at a certain angle, depending of many factors.

Yes, you can't predict it, sorry made a mistake. And yes Flex, pitch angle should be around 25 degrees, as you can't go how higer than 30 degrees for the A330- 33 degrees for the 320.

If you don't have AoA protection, you are not in normal law.

Why are you saying that I am wrong here?

It is just smart cockpit! And Flex added details too...

[LHookins 3,102]

Thanks, Rob.  Pitch attitude does make more sense, and I was wondering if that was a typo, but why not just say pitch?

 

 

 

Why are you saying that I am wrong here?

 

Mostly that you could memorize whatever document you have in front of you word for word and still not know anything about the subject. There are a lot of prerequisites that you're expected to know before you even start reading, and you don't know these.  A lot of people have given you a lot of advice about where to start so that you can be in the right place to start reading the FCOM.  As it is, you don't even know what questions to ask and then don't understand the answers.  Don't worry, you'll get it eventually, but you'll need to learn some basics.  Without the basics, whatever you do learn, a lot of it will be wrong, even if it's word for word from the manual.

 

Hook

[Dave Morgan 68]

I'll say it again...

 

Get yourself down to your local airfield. At nearly 14, you probably need to lean on your folks to take you there but they might enjoy it too. If they can afford it, ask them for a trial flying lesson for your birthday.

 

D