PDA

View Full Version : A320 Autothrust


Sahil Verma
25th Apr 2010, 12:33
Hi....I am a fresh Australian and Indian CPL holder with 213 hrs of experience.
I look forward to flying an A320 someday...The thought of the auto throttle fascinates me...I do not possess much knowledge about it though...
I had some doubts, out of curiosity, regarding the plane though...

Do the computers int he aircraft calculate the V speeds(V1, V2, etc) for every flight according to the ambient weather and loading conditions and display them on the PFD or they remain fixed values..??

When we change the the attitude of the aircraft, does the auto throttle adjust the power of the engines to maintain the airspeed/mach no. ?

Does the throttle lever move or does it stay fixed when auto thrust is in operation??

During landing, do we set the Auto throttle to the approach speeds or do we manually control the throttle?

Flying the aircraft manually at high speeds will cause discomfort to the passengers behind...at what time do we first enable the autopilot???

These questions may seem really silly to those for whom flying this plane is part of their everyday life, but i'd really appreciate it if somebody answer them for me. thank you,



cheers,
Sahil

Wally Mk2
25th Apr 2010, 14:56
You have a lot of Q's there may I suggest purchasing a book that is great reading & all about the A320 especially for those that are not too familiar with the Airbus way of doing things. Book is the "unofficial Airbus A320 Simulator & CheckRide Procedures manual" by Mike Ray, A UAL: Capt. This book will answer all yr questions & some!
fascinating reading for the laymen as well. Do a Google search with the Capt's name with perhaps the words UTP (University of Temecula Press)
Cost is around $US90 & worth every cent:ok:

Wmk2:-)

DesiPilot
26th Apr 2010, 03:08
Sahil.

You can go to http://airbusdriver.net and download technical notes from there. You can also try www.smartcockpit.com and download FCOM from there, specially FCOM I and read the chapter on Autoflight.

To answer your questions:

1) NO, you have to calculate it either from the hard copy of RTOW charts for the particular runway or from a software inserting the ambient conditions or worst case scenerio from the FCOM 2.

2) Yes.

3) Thrust lever is fixed in CL (climb) gate and Auto thrust can change power anywhere between idle to climb (assuming no single engine operation, during single engine it is kept in MCT and thrust can vary between idle and MCT).

4) No, autothrust manages the thrust to maintain speed.

5) Flying the aircraft manually does not cause discomfort to passengers, it all depends on your flight techniques and smoothness, the earliest the airbus pilot can engage autopilot is at minimum 100' RA and min 5 sec after liftoff (both conditions must be met).

Sahil Verma
26th Apr 2010, 07:35
Thank you.That clears many of my doubts.The thought of transition from such small piston aircraft to giant jets seems weird..I really appreciate both your replies. The air bus seems really fascinating. I recently watched a video where the aircraft would itself roll out of steep banks and recover from stalls..
I will definitely purchase "The unofficial Airbus A320 Simulator & CheckRide Procedures manual" but from a book store. It is also recommended in "www.airbusdriver.net"..I hope to undergo Type Rating on it soon..
Both the websites are really informative..Thank you so much..

Cheers,
Sahil

fredgrav
26th Apr 2010, 08:13
Do the computers in the aircraft calculate the V speeds(V1, V2, etc) for every flight according to the ambient weather and loading conditions and display them on the PFD or they remain fixed values..??

Hi SAHIL,
FMGC (Flight Management and Guidance Computer) computes takeoff, approach and go-around speeds based on the actual "operational environment" (weather, weight, conf etc.) as well as Flight Augmentation Computers (FAC's) do in calculating minimum and maximum speeds, maneuvering speeds etc. Nowdays a TOS (Takeoff Securing Functions) is being implemented on new Airbus a/c, whose purpose is to automatically check consistency of several take-off parameters, inserted into the FMGC.

When we change the the attitude of the aircraft, does the auto throttle adjust the power of the engines to maintain the airspeed/mach no. ?

In very short form, there're 2 ATHR modes: MACH/SPEED mode and THRUST mode, so it depends on what mode is active at the moment.

Does the throttle lever move or does it stay fixed when auto thrust is in operation??

It does not move on Airbus, as a matter of fact it is an Autothrust Sys and not Autothrottle Sys.

During landing, do we set the Auto throttle to the approach speeds or do we manually control the throttle?


It depends on whether the ATHR is active or not.

Flying the aircraft manually at high speeds will cause discomfort to the passengers behind...at what time do we first enable the autopilot???

Autopilot damps oscillations and, most of the times, is far more accurate than pilot itself: thus usually hand-flying turns out to be less comfortable than auto-flight. On Airbus, autopilot is normally available 5 seconds after lift-off (100 ft) then it can be engaged right away: though the MIN ALT for AP engagement changes with every Company's SOP.

Hope this helps,
fredgrav

Sahil Verma
26th Apr 2010, 16:26
Thank you Sir,
I really appreciate your taking out valuable time for this..

So does that mean that the V1, V2 speeds, etc ,displayed on the ASI in the PFD will be different every time we take off..?

Also, out of interest, is it easy to maintain DME arcs manually at jet speeds during instrument approaches..??

And since you are carrying passengers back there, you hardly get more than one chance on landing the plane.If you are asked to conduct a visual approach during the day without the ILS, i believe that your judgement cannot be less than perfect. True?

fredgrav
26th Apr 2010, 21:56
So does that mean that the V1, V2 speeds, etc ,displayed on the ASI in the PFD will be different every time we take off..?

Yep, they are !

is it easy to maintain DME arcs manually at jet speeds during instrument approaches..??

Bear in mind that a DME arc is nothing more than a simple turn made to keep a constant distance from a navaid while flying around it and conducted at low angles of bank: a very simple manoeuvre in itself and couldn't be any easier by using RMI ... though, the higher the aircraft speed the faster should be your response to keep distance constant.

If you are asked to conduct a visual approach during the day without the ILS, i believe that your judgement cannot be less than perfect. True?

There're different types of approach you may conduct under IFR beyond ILS: eg. IGS, LOC, VOR, LCTR, RNAV etc. If you're circling or just asked ATC for a visual, the landing runway must be in sight and must remain as such throughout the entire manoeuvre. Your judgement on either the horizontal or vertical path is often improved by using AFDS functions like FPV (Flight Path Vector) and visual guidance systems like PAPI, VASI, LDIN lights etc. A jet aircraft has a relatively low response time on thrust changes and its handling characteristics are different from situation to situation: basically, it's a bit trickier to fly a jet than a piston/props.

Hope that helps,
fredgrav

Sahil Verma
27th Apr 2010, 08:48
Actually, it does help....Thank you so much..
That actually clears most of my doubts..Ill let you know in case I have more doubts...Thanks again



cheers
Sahil