Brunswick737 From United States of America, joined Oct 2003, 400 posts, RR: 0 Posted (9 years 6 months 1 day 6 hours ago) and read 4204 times:
I just downloaded a ton of airbus & boeing cockpit videos and during the landing phase when it goes 50,40,30,20,10 then the voice says "retard" a couple to times before touchdown, then when it stops, the plane touches down. I viewed the boeing cockpit landings and I dont here the "retard" after the countdown...I was wondering what is that for and why boeing does not have that "word" before touchdown????????????
AJ From Australia, joined Nov 1999, 2376 posts, RR: 27 Reply 2, posted (9 years 6 months 1 day 4 hours ago) and read 4124 times:
When being manually flown most Boeing types are no longer using the autothrottle so speed and power is under the control of the Pilot Flying.
On the Airbus the autothrottle provides speed control on finals, with the thrust levers remaining stationary. When the RETARD call is made the thrust levers are retarded from the climb detent to allow idle thrust to be achieved at the expense of the commanded speed for landing.
Mr.BA From Singapore, joined Sep 2000, 3423 posts, RR: 23 Reply 3, posted (9 years 6 months 1 day 3 hours ago) and read 4112 times:
Is it to say that the thrust levers on Airbuses are nothing like Boeing in the sense of moving freely? I understand that Airbus throttles don't really move along with the spooling up/down of the engines. Does the throttle lever stay stationary at CLB Detent when thrust is reduced upon levelling at cruise altitude and stays at that position until the computer calls for "Retard" just before touchdown (assuming autothrust is used all the while)?
I've read that before you can actually disconnect the autothrottle you have to manually pull the thrust levers to the corresponding thrust at that point of time (there's a pointer at the engine gauges?)? How do you do it, if the throttles can only be operated and moved between "gates"?
Mandala499 From Indonesia, joined Aug 2001, 6209 posts, RR: 74 Reply 4, posted (9 years 6 months 1 day 1 hour ago) and read 4096 times:
I thought the Airbus Autothrottles have to be in the CLB/AT position or above (eg. TOGA or FLX for take off mode, CLB/AT for other modes) for the Autothrottle to be engaged? So moving it below the CLB/AT (eg. hit the IDLE) position, not anywhere in between) will disconnect the A/T and let the engines go to idle for the touchdown. You can power up the engines again (for whatever reason) manually after that...
What I'm not sure is what if you don't hit the idle detent? Will it disconnect? Or press the A/T D/C below CLB/AT detent?
Mr.BA, yes, those throttles don't move along like the Boeings, which does not allow manual intervention with the exception of A/T D/C or TO-GA. To disconnect, you need to "sync" the throttle to the corresponding power setting then press the D/C... or just hit idle... (not sure about this last bit).
For Boeings, throttle move along with the thrust setting at all times, under manual or auto throttle. This would give the pilot some comfort if the A/T becomes slow to react... which CAN (not always does) happen. You can manually intervene and then let go of the throttles and it'll settle according to the A/T.
Not saying one is wrong and the other is right, just a different mode of operation and a different logic.
AJ, in Garuda, the pilots fly with A/T on full time in their SOP. A/T landings require manual intervention to idle the engines in both the bus and the boeing when flaring.
Computer: "50, 40, 30, 20, RETARD"
PF: "Going around! TOGA!"
PNF: "Going around aye, TOGA set, positive climb... flap2"
PF: "Gear up..."
PNF: "Gear up aye... by the way, why go around?"
PF: "Who does it think I am calling me RETARD?"
When losing situational awareness, pray Cumulus Granitus isn't nearby !
Mr.BA From Singapore, joined Sep 2000, 3423 posts, RR: 23 Reply 5, posted (9 years 6 months 1 day ago) and read 4080 times:
I've read up quite a bit on the throttles of Airbuses. I'm still pretty confused and I can't figure out what did Airbus based on to have this logic of operation? I'm not saying it's wrong or it's not desirable, but why this logic? What did they have in mind when they designed this?
Again I feel it's more logical to have the throttles moving with the engines to enable pilots to have 'direct feedback' and direct reference as to which level of thrust the engines are at... etc. I'm not bashing Airbus but am just pretty curious on how they did come up with this idea?
MD11Engineer From Germany, joined Oct 2003, 13368 posts, RR: 64 Reply 6, posted (9 years 6 months 23 hours ago) and read 4072 times:
They made the system simpler. On Boeing aiircraft you´ll have an auto throttle actuator for each thrust lever beneath the center pedestal, which is controlled by the auto throttle computer and in turn moves the thrust lever. The thrust levers in turn control the engine power. I think it is a left-over from the old days of mechanical control of the engines through cables and pulleys. Today on electronic engines the thrust lever operates a thrust lever angle resolver (TRA), which sends an electric signal to the engine EEC. Instead of going the detour of moving the throttle mechanicaly to control the TRA resolvers and THEN sending an electric signal to the engines, Airbus sends the signal directly from the flight control / auto thrust computers to the engine EECs.
The drawback is that the pilot can´t see with a glance at the thrust levers what the engine power setting is. I think it takes some time to get used to. The MD-11 used a similar system as Boeing.
AJ From Australia, joined Nov 1999, 2376 posts, RR: 27 Reply 7, posted (9 years 6 months 23 hours ago) and read 4064 times:
Mandala499, landing with the autothrottle engaged in a Boeing will cause the Master Caution 'AUTOTHROTTLE' to appear when reverse is selected after touchdown, that's after forcing the thrust levers closed as the servos will try increase thrust to maintain commanded speed except in an autoland. It seems odd that Garuda has this battle on every landing!
Slamclick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 8, posted (9 years 6 months 18 hours ago) and read 3983 times:
When, during landing, the Airbus annunciates "retard" it does so twice as a verb, after that it is a noun.
Minor correction here. The airbus thrust levers can be set anywhere but if they are not set in the appropriate detent the system will remind you to move them. The autothrottle system has authority from just above an idle up to the position set by the thrust lever - even if the lever is not set in a detent. There is a small green (I think-don't have one in front of me) donut on the N1 gauges that show Thrust Lever Angle.
Therefore, for a full thrust takeoff you would set TOGA. For a reduced thrust takeoff you would set FLEX/MCT. Which would give thrust based on the assumed temperature up to the flex power setting or maximum continuous. Either way, at acceleration height after takeoff the system will annunciate "LVR CLB" and you need only move the lever back to CLB position. If you must level off at low altitude, say 2000' the command bars will guide you through the pushover to level off and the engines will automatically throttle back to maintain the speed limit for configuration/altitude.
It is a great system but it sure could make you lazy.
Happiness is not seeing another trite Ste. Maarten photo all week long.
Mandala499 From Indonesia, joined Aug 2001, 6209 posts, RR: 74 Reply 9, posted (9 years 6 months 18 hours ago) and read 3988 times:
I only had a brief look at GA's manuals... But approaches are to be done with auto throttle...
On the 737s, it appears that for single channel autoapproach, A/P should be disconnected at DH or prior to 50ft whichnever is higher, then the A/T will announce FLARE at 27ft RA and closes the throttles in 6 seconds, then disengages 2 seconds afterwards.
Anyways, had a quick call to check it and I seem that they D/C A/T prior to flare anyways... "best to make sure it goes to idle when you want it to"... and to prevent such battles you mentioned...
Thanks for spotting what I overlooked...
When losing situational awareness, pray Cumulus Granitus isn't nearby !
N243NW From United States of America, joined Jul 2003, 1502 posts, RR: 21 Reply 10, posted (9 years 5 months 4 weeks 6 hours ago) and read 3778 times:
Just a cool tidbit of information about the 'Bus aural warning system:
The altitude callouts are made from 50 to 20 feet, upon which "Retard" is said repetedly until the pilot closes the throttles. Once this is accomplished, the computer tells the pilots the current radio altitude. It would go something like this: fifty....fourty.....thirty......twenty..retard..retard..ret-eight........[touchdown]
I posted this question a while ago and never got an answer. On final, why do some Airbuses say weird R/A callouts like "two hundred and thirty"? Is this just different airlines having the computer programmed differentyl? Correct me if I'm wrong about any of this.
AM From Mexico, joined Oct 1999, 578 posts, RR: 2 Reply 12, posted (9 years 5 months 3 weeks 6 days 17 hours ago) and read 3698 times:
AJ, how are you?
I was reading a topic on PPRuNe.org the other day about different company procedures regarding autothrottle use during manual approaches/landings. Most of the pilots participating fly 737s, but I think it's somehow similar on the 757/767. When you disconnect the A/P, do you disconnect A/T right away, or do you leave it engaged until just before flaring? Or is it up to the PF?
I was allowed to jumpseat in a Mexicana 757 on September. When landing in MEX, I noticed the captain disconnecting the A/T more or less at the 100ft call (which by the way was made by the PNF, since there were no callouts after inhibiting the "G/S" warning). He just had to retard and that was it.
And something off topic (sorry), but that has to do with the same landing. Speed brakes were armed, but didn't deploy upon main gear touch down. Before nose wheel touch down, the PNF called out something like "Spoilers not deployed!", and was very quick to manually extend the speed brakes. What's the reason for this? Does that happen often? The captain was like "NO, NO!", but it was too late and bam!, a very hard nose wheel slam into the ground. After vacating the runway, the captain told the FO he preferred not to deploy spoilers immediately after touchdown, conditions permitting, because it was much more gentle to do that manually once with all wheels on the ground.
"... for there you have been and there you will long to return."