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A320 Real World Guidance And Tips


Wayne Klockner

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Wayne Klockner

This thread serves as a repository of guidance, tips, and real world advice for piloting the A320 gleaned from the real pilots who've posted such on this board and who've helped make this simulation the finest of its kind. Please PM me with any corrections, suggestions, and additions, or alternatively, add those to this thread, and I'll update this initial posting with them. I'll attribute all content unless you feel otherwise, and I will edit slightly content for clarity and brevity.

Managing Descents by X24 (Christopher Allan)

60T GW is a convenient median value, above which we know we're starting to feel the weight more and all that implies. We make a point of mentioning that fact during the arrival briefing - gets harder to slow down if you have a tailwind at the top of the ILS for instance, which is pretty typical around Melbourne. Vls can be a problem if you haven't anticipated this - she won't go down and slow down so you have to get in early. Then there's short runways = hot brakes, etc.

Conversely, below 60T, lighter, don't mind so much when ATC asks you maintain 180 kts till 6 miles, clattery landings, cooler brakes, quicker to turn around 'cos not so many passengers so the cabin crew are a little less frazzled, and it means the weather's good 'cos we have less fuel remaining.

Because you only get half speed brake with the autopilot engaged, you can disengage the AP, use full speed brake, then re-engage the AP. Done that a few times. Here are some numbers most of my colleagues seem to use to assess how the descent profile is looking. Once you get used to this you can tell quite quickly if you're starting to get high or low or it looks like you're going to. We don't necessarily always trust the flight guidance implicitly, and these are really useful raw data gross error cross-checks.

In round figures, 1000/IAS = miles per thousand feet. So at 300 knots, very close to 3 miles per thousand (3.3), at 250 knots - 4 miles per thousand, and 200 knots - 5 miles per thousand. Those are easy to do in your head. That's clean - 200 will be pretty close to green dot at medium weights. As you slow down, the glide flattens out. Green dot is best lift/drag speed. They say it takes a mile in level flight to lose 10 knots, bit less if you're light.

From 10,000 ft, a 4x profile works really well for the A320, i.e. 4 x the alt in 1000's of feet, so at 5000' you want to be at 20 miles, 4000 at 16, 3000 at 12-13 and aim for green dot at 13 miles.

This makes it easy to see if you're getting high or low. If low, we might VS it to match the blue bottom of descent arrow with the white continue descent arrow. If high, so OP DES, tweak the speed up a few knots, bit of speed brake, watching the blue arrow to see where bottom of descent will be so as to try and have a bit of a level segment to wash the speed off rather that try to do it while descending. In rare cases, getting slowed down and held up because of traffic, I've had flaps 1 out at 7000 feet.

We'll be around 17 miles out doing 230, when ATC tells us to reduce to 190. As soon as the brakes are out (and remember you only get half deflection with the AP engaged), the Vls begins to climb and as it reaches our indicated speed of 230 we back the brakes off a bit to control the Vls, and once below 230 knots, select flaps 1 which then causes Vls to quickly reduce.

Managing Descents (2) by Aerlingus231

Managed descents are a quite inconsistent to be honest. As a rough guide, it responds slowly initially to deviations but then will progressively reduce the pitch up to the point where it'll quite happily put you in a dive of death in excess of -4500 fpm with no qualms to try and regain the computed profile. Descents are quite the dark art in the A320, In most jets to be fair, the computer will only roughly put you in the ball park and will quite often need intervention in the form of VS/Op Des and manually adjusting the speed to accurately manage your profile.

Entering the actual spot winds on the way down can help, particularly in the case of tailwinds on the descent. But invariably, most of the time, the winds we have are spaced in gaps of 8,000' +, and the computer will consider that the wind changes evenly across those 8000' from the first level to the next. In reality, the swing tends to happen across 2,000-3,000', meaning the computer gets a bit of a surprise, and in turn, gives us a bit of a surprise with its attempts to regain the profile. I agree with the general concept though that it does reduce the severity of its inconsistencies and does better plan the track millage required for the descent.

Managing Descents (3) by X24 (Christopher Allan)

To comply with ATC speed requirements, I generally select the speed (rather than MACH), especially below the Mach/SPD crossover altitude. SPD rather than MACH also makes it easier to achieve RTAs accurately.

Once the winds have been put in, it gives the FMGS a forecast cross-section of the atmosphere for predictions - the operative word being "forecast". A managed descent out of a 160kt tailwind that suddenly drops off can result in an over-speed if you're not ready for it, and the aeroplane will quite happily allow this. Surprisingly given that it is fly-by-wire, i.e. software-driven, there are noticeable differences between airframes when it comes to speed handling. If high on profile with speed and descent managed, some aircraft will put their heads down and allow the speed to overshoot the top end of the buffer and get right up to the bottom of the "bricks", still accelerating. Speed-brake is usually enough to prevent an over-speed and cause the nose to pitch up and the speed to decay if you get in early. Otherwise, I've seen people have to disconnect, close the thrust levers and manually level off. This can all happen very quickly, particularly at higher altitudes, especially descending out of a strong tailwind that reduces rapidly with altitude. I typically start descent 5-10 miles early, which starts off nice and gentle at 1000 fpm and with no surprises.

Also, being within 2-300' of an altitude restriction on a STAR is considered satisfactory by the aircraft. Accordingly, to meet a limiting STAR requirement of at or below 9000', I put in -8700. Murphy's Law states that if you don't amend the altitude, it will go through at 9300 feet, and if you do, it will go through at 8700 feet!

Managing Descents (4) by Flyingspanner

On the A320, when managed descent is initiated before the calculated descent point, the aircraft will put you into a 1000ft/min descent until the calculated rate meets the current profile for the descent. The aircraft will then adjust its thrust for the descent mode. The FMA call for this on the A320 is "THR IDLE" - HOWEVER, this is not actually a true statement. Actually, some thrust is kept on to maintain the descent profile and keep the green profile dot in the middle. This can cause speed to build up to almost reaching the descent speed +20 upper band (around the +15-17 mark). it is only then that the the engines actually go back to an idle setting, confirmed by the flashing IDLE on the Upper ECAM in-between the 2 engine EPR displays. Once it reaches this point, the aircraft then tries to slow down and maintain the calculated profile, slowing down to the target airspeed, sometimes with varying degrees of accuracy depending on the descent winds etc.

Lastly, in the airline I work for, we are using a variable cost index, which alters the descent speed. For example, a CI of 50 gives a descent speed of around 320kts. If you are kept high (by ATC), this does not give much speed allowance to make a fast descent to regain the profile. I generally like to use a descent speed of around 290kts. That way if kept high, I can go fast to get down and then slow down (my old instructor used to say: "its easier to go down, then slow down than to slow down and go down!" We also use an Idle Performance percentage to reduce the computed track miles for descent on the profile by about 15 miles to try and maintain a higher altitude for longer before the descent.

Managing Descents (5) by X24 (Christopher Allan)

Fuel is a huge cost to us, so we operate at CI 15, and depending on weight and wind, the FMGS will often program a descent speed of .76 - .77/270 - 280. If less than 280 knots, company policy is to enter /280 on the DES PERF page. Descending early, say 5 - 10 miles, initiates a descent at 1000 fpm. The behavior of the thrust depends on whether the descent winds have been entered and how the actual winds compare to the entered winds. The FM uses this to decide if it is high or low and adjusts thrust and/or pitch accordingly. If low, the speed will tend to reduce to the bottom of the speed bracket - target minus 20 - but because ATC expects us to maintain a certain speed, we generally then select 280, or 250 if below 10,000'.

Initially, when commencing the descent, thrust will reduce to idle to stop the aircraft accelerating, but once the FM has had a chance to evaluate the profile, thrust may well increase again. In a managed descent, the FMA quite often flickers between THR IDLE and SPEED as it tries to maintain the profile and the programmed speed.

Managing Crosswind Landings by Bus_Driver

I keep the crab all the way until about 30 feet, then kick it straight with rudder (if it's really strong leaving 5 degrees crab on touchdown) simultaneously when bringing out the crab applying enough sidestick to prevent the wing lifting. Again, if the wind is really strong, i keep about 5 degrees drift and a small amount of wing down at touchdown.

Once on the ground the aircraft tends to track down the runway pretty easily, and is easily controlled with the peddles. The autobrake makes our life easier (particularly in the simulator); in real life it seems to want to stay straight better than in the simulator.

PS: you see a lot of people saying the airbus is tricky in a crosswind, personally I have not found this to be the case - even in a maximum crosswind (38kt)

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Christopher Allan

@AerLingus231

I agree. To comply with ATC speed requirements I generally select the speed, especially below the Mach/SPD crossover altitude. SPD rather than MACH also makes it easier to achieve RTA's accurately.

Once the winds have been put in, it gives the FMGS a forecast cross-section of the atmosphere for predictions - the operative word being "forecast". A managed descent out of a 160kt tailwind that suddenly drops off can result in an over-speed if you're not ready for it, and the aeroplane will quite happily allow this. Surprisingly given that it is fly-by-wire, i.e. software-driven, there are noticeable differences between airframes when it comes to speed handling. If high on profile with speed and descent managed, some aircraft will put their heads down and allow the speed to overshoot the top end of the buffer and get right up to the bottom of the "bricks", still accelerating. Speed-brake is usually enough to prevent an over-speed and cause the nose to pitch up and the speed to decay if you get in early. Otherwise, I've seen people have to disconnect, close the thrust levers and manually level off. This can all happen very quickly, particularly at higher altitudes, especially descending out of a strong tailwind that reduces rapidly with altitude. I typically start descent 5-10 miles early which starts off nice and gentle at 1000 fpm and no surprises.

Also, being within 2-300' of an altitude restriction on a STAR is considered satisfactory by the FM. Because of this, to meet a limiting STAR requirement of at or below 9000', I put in -8700. Murphy's Law states that if you don't amend the altitude, it will go through at 9300 feet, and if you do, it will go through at 8700 feet! Go figure...

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Flyingspanner

Further To Managed Descents:

Hi guys, im sure that there are some real world pilots here so will keep it as I see it, please advise if anyone else has any different observations on their aircraft.

On the A320 when managed descent is initiated the aircraft if before the calculated descent point will put you into a 1000ft/min descent until the calculated rate meets the current profile for the descent and then the aircraft will adjust its thrust for its descent mode.

The FMA call for this on the A320 is "THR IDLE" - HOWEVER this is not actually a true statement. Some thrust is actually kept on in maintaining the descent profile keeping the green profile dot in the middle. This causes the speed to build up to almost reaching the descent speed +20 upper band (around the +15-17 mark). it is only then that the the engines actually go back to an actual idle setting confirmed by the flashing IDLE on the Upper ECAM in-between the 2 engine EPR displays.

Once it reaches this point the aircraft then tries to slow down and maintain the calculated profile going down and slowing down to the target airspeed. Sometimes with varying degrees of accuracy depending on the descent winds etc.

in fact, Airbus for the A330 actually added another FMA Mode Called "THR DESC" when entering descent and the thrust not at the idle setting.

I am not entirely sure as to why the aircraft does this but I will attempt to find out if there is a logic for this from Airbus.

Lastly in the airline I work for we at present are using a variable cost index which alters the descent speed, for example a CI of 50 gives a descent speed of around 320kts, this does not give much speed allowance if you are kept high to make a fast descent to regain the profile. I generally like to use a descent speed of around 290kts that way if kept high I can go fast to get down and then slow down (my old instructor used to say: "its easier to go down then slow down than slow down and go down!" We also use an Idle Performance percentage to reduce the computed track miles for descent on the profile by about 15 miles to try and maintain a higher altitude for longer before the descent..

Has anyone else found this to be true for their company?

regards

John

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Christopher Allan

Has anyone else found this to be true for their company?

Yes. Fuel is a huge cost to us so we operate at CI15 and depending on weight and wind, the FMGS will often program a descent speed of .76 - .77/270 - 280. If less than 280 knots, company policy is to enter /280 on the DES PERF page. Descending early, say 5 - 10 miles, initiates a descent at 1000 fpm. The behaviour of the thrust depends on whether the descent winds have been entered, and how the actual winds compare to the entered winds. The FM uses this to decide if it is high or low and adjusts thrust and/or pitch accordingly. If low, the speed will tend to reduce to the bottom of the speed bracket - target minus 20 - but because ATC expect us to maintain a certain speed, we generally then select 280, or 250 if below 10,000'.

Initially, when commencing the descent, thrust will reduce to idle to stop the aircraft accelerating, but once the FM has had a chance to evaluate the profile, thrust may well increase again. In a managed descent, the FMA quite often flickers between THR IDLE and SPEED as it tries to maintain the profile and the programmed speed.

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