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Hydraulic system loading

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Hydraulic system loading

Old 3rd Jan 2022, 05:11
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Even in B747 classic we ordered gear down and Flap3 together but with a rider " gear down when three greens flaps 3
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Old 3rd Jan 2022, 09:46
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I think you may be taking an overly prescriptive view of what’s written in the SOP. Our manual says to turn the speaker on to do the oxygen check. It doesn’t say to turn it back off. I don’t take that to mean we have to fly with the speaker on.

I agree that “nothing’s happened yet” is by itself not necessarily a solid argument, but coupled with the facts that Airbus hasn’t listed a specific limitation against it, I think it’s fine.

I’m willing to reverse my stance if there’s any technical word from Airbus against doing so though.
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Old 3rd Jan 2022, 12:56
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Airbus training power point
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Old 3rd Jan 2022, 15:14
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Isn't it also good airmanship to only change 1 configuration at a time?

Flap 2 - balloon - trust back - trim forward
Gear down - more drag - trust up - trim back
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Old 3rd Jan 2022, 18:45
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Originally Posted by cav-not-ok View Post
Isn't it also good airmanship to only change 1 configuration at a time?

Flap 2 - balloon - trust back - trim forward
Gear down - more drag - trust up - trim back
How about trim and/or pitch down before the balloon so it doesn't happen in the first place?

Then, if pitch/drag effects of simultaneous config changes are known ahead of time, they can be counteracted simultaneously ahead of time, too.
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Old 4th Jan 2022, 00:57
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Originally Posted by vilas View Post

Airbus training power point
I see what you're trying to say, but this is just a repeat of the SOP.

You point to the fact that it says "when gear is down". There's an argument to be made for that logic, but I'll reiterate, if there was an actual danger in moving the gear and flaps simultaneously, they'd have put that in the limitations chapter. They found time to include a maximum speed in a turn above 76T. The navigation section of the limitations chapter if full of both esoteric, and general limitations. I find it difficult to believe that moving the gear and flaps simultaneously cases undue stress, and they didn't include it in the limitations section.

Worth noting that for GA, it doesn't say to wait for the flaps to lock before raising the gear. Surely raising the ear puts more stress on the system than lowering it.
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Old 4th Jan 2022, 02:24
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The point I am making is Airbus says so and teaches it so. You can't say they don't. On the other hand no ​where is it written that gear and flaps can be taken at the same time. There are a few thing which may not be limitations but good practices. Ask Airbus on techrequest if you want to do differently. Settings heading ang pulling or pulling first and setting the heading. People find no difference and yet Airblue captain in circling approach under pressure of marginal weather kept dialling and then pulled and aircraft turned shorter way into the hill 160 people lost their lives. Making procedures in FBW is not line pilot's job.

Last edited by vilas; 4th Jan 2022 at 04:04.
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Old 4th Jan 2022, 05:27
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Vilas, any chance you can ask Airbus about it?
I personally always wait for the gears and doors to be locked before asking next notch of flaps unless I find myself in a situation where I screwed up and configured too late. Otherwise, there is no rush to set flaps while gears are still in transit.
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Old 4th Jan 2022, 09:03
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Good practice to do one major thing at a time, so that pilots can confirm correct selection, correct movement and correct final position. If you get an uncommanded roll after dropping gear and flap together. which service is causing the uncommanded roll?

No need to rush in aviation if you are doing it right. So why put your hydraulic system to maximum load if you don't need to? A good pilot will respect their aircraft mechanisms.

In a go-around, as you know, the call is "Go around, flap" <select flap> then read out FMA. Then PM will call "positive climb", then PF will call "gear up", <select gear-up> , so the two things are not simultaneous and by the time the gear is called for the flaps will have finished moving.
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Old 4th Jan 2022, 13:36
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Originally Posted by pineteam View Post
Vilas, any chance you can ask Airbus about it?
I personally always wait for the gears and doors to be locked before asking next notch of flaps unless I find myself in a situation where I screwed up and configured too late. Otherwise, there is no rush to set flaps while gears are still in transit.
That's the correct way of doing. That's the way Airbus teaches. Gear is a heavy user, no manufacturer recommends gear+flaps with flight controls requiring hydraulics as well. In Airbus selecting Flaps2 moves slat from 1 to 2 but the flaps a long way from 0 to 2 if gear is also lowered it definitely increases demand on the system. Similarly when gear is going down the doors are open and the drag is high till they close adding to it flap3 doesn't make sense. It will be nice if someone can produce something more than I do it.

Last edited by vilas; 4th Jan 2022 at 14:39.
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Old 4th Jan 2022, 15:24
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Originally Posted by aeromech3 View Post
Swash plate pump? higher demand higher angle of plate, more friction on slipper pads, case drain filter blockage, more flow generates more heat; excessive high system demand can lead to knock / vibration; jerky operation of hydraulic motors can exacerbate drive shaft wear and cause system lock out ( mainly flaps). Could cause priority valves, where fitted, to hammer leading to such items as extending gear extension time, longer unclean door configuration flight mode.
This is the kind of answer I was looking for Aeromech, so thanks. Looks like there's a whole lot more going on than just "pumping against the same or lower pressure."
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Old 4th Jan 2022, 16:51
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Quote :
WHEN LANDING GEAR IS DOWN

FLAPS 3 ...........................................ORDER
FLAPS 3 ............................................SELECT

Check Airman : I don’t read that as “wait for three greens to move the flaps”.

Are you sure ? "WHEN" seems fairly clearly to be a conditional clearance, relying on something else having finished first, in this case the landing gear being down. i.e. you wait until the landing gear is down before moving the flaps further. How do you know the landing gear is down? = you have three/four green lights on the Gear panel and/or at least three/four green triangles on the Wheels page.
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Old 5th Jan 2022, 23:48
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I typed up a much longer response, but it got lost in the ether of the internet.

I'll skip to the good part. If Airbus can answer the question of whether there are any short or long term negative effects of moving flaps and gear simultaneously, I'll be happy to change the way I do things.
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Old 6th Jan 2022, 08:20
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Originally Posted by Uplinker View Post
Quote :
WHEN LANDING GEAR IS DOWN

FLAPS 3 ...........................................ORDER
FLAPS 3 ............................................SELECT

Check Airman : I don’t read that as “wait for three greens to move the flaps”.

Are you sure ? "WHEN" seems fairly clearly to be a conditional clearance, relying on something else having finished first, in this case the landing gear being down. i.e. you wait until the landing gear is down before moving the flaps further. How do you know the landing gear is down? = you have three/four green lights on the Gear panel and/or at least three/four green triangles on the Wheels page.
I actually agree with most of you guys ,especially with Vilas, and disagree with Check Airman.
Configuration Management chapter is quite specified , WHEN sounds quite conditional. And it seems very strange that you read it in another way. So you want them to write it in a way : "Please wait until gears are dn"? So tonight I'll make techrequest about it
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Old 6th Jan 2022, 14:07
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We sent a Tech Request a while ago and this is what Airbus said about this topic (320 family; there are other reasons to select gear down as per SOP on, say the 350, e.g., for the PLT to finish before landing):
The SOP philosophy regarding landing gear extension is to get it down and locked before reaching the final landing configuration. As either CONF FULL or CONF3 may be used for the landing, the SOP therefore requires selecting the landing gear down before selecting FLAPS 3, in order that landing gear extension is independent from the final selected landing configuration. This SOP recommendation was established to cope with the fact that the "L/G: GEAR NOT DOWN" red warning is triggered if the aircraft comes down to 750 ft radio height, with landing gear lever not in the down position. Indeed, if this SOP recommendation is not followed, i.e. if, for example, the landing gear and flaps 3 are selected simultaneously, and if the flaps/slats extension sequence is started a bit late, the landing gear selection may be close to this altitude threshold. Another point is that the L/G: GEAR NOT DOWNLOCKED warning is triggered if the landing gear extension sequence is not completed after 30 seconds: thus, selecting the L/G down after flaps 2 extension allow a comfortable reaction time, in the event that the warning is triggered. Finally, for each SLATS/FLAPS setting, the autotrim function trim the aircraft. The same applies when the landing gear is set to down. Waiting the landing gear is down locked before selecting Conf 3 allows getting the aircraft trimmed before a new SLATS/FLAPS configuration.

For all these reasons, we recommend to select the landing gear down before selecting FLAPS 3. However, there is no technical objection for selecting CONF 3 or CONF FULL before L/G extension sequence as long as the maximum speeds to operate SLATS/FLAPS and L/G are respected.
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Old 6th Jan 2022, 14:46
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Sideline gripe on linguistics and not hydraulics. I read this sentence: "The SOP philosophy regarding landing gear extension is to get it down and locked before reaching the final landing configuration." and thought WTF kind of sentence is this, the gear is down before you're in landing configuration by definition, there's no logically possible way to have this problem to need avoiding. Gear up in landing configuration is an oxymoron.

Well, the context of the rest of the paragraph sheds light on that "configuration" here means flaps. OK, but we already have a word for that: "flaps!" Now, we're sacrificed a perfectly useful word (configuration) at the altar of long and impressive technical words for ornamentation... we can be in "final landing configuration" but land gear up

(Oh, maybe they wanted that to specify flaps AND slats, not to be confused with flaps only? To avoid the mass confusion and chaos of every other airplane that just calls it "flaps" and everyone understands that it includes both? How about, oh, "flaps/slats" which still leaves "configuration" to mean that you can be configured for landing and have a normal safe landing?!)

​​
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Old 6th Jan 2022, 14:52
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Originally Posted by Vessbot View Post
Sideline gripe on linguistics and not hydraulics. I read this sentence: "The SOP philosophy regarding landing gear extension is to get it down and locked before reaching the final landing configuration." and thought WTF kind of sentence is this, the gear is down before you're in landing configuration by definition, there's no logically possible way to have this problem to need avoiding. Gear up in landing configuration is an oxymoron.

Well, the context of the rest of the paragraph sheds light on that "configuration" here means flaps. OK, but we already have a word for that: "flaps!" Now, we're sacrificed a perfectly useful word (configuration) at the altar of long and impressive technical words for ornamentation... we can be in "final landing configuration" but land gear up

(Oh, maybe they wanted that to specify flaps AND slats, not to be confused with flaps only? To avoid the mass confusion and chaos of every other airplane that just calls it "flaps" and everyone understands that it includes both? How about, oh, "flaps/slats" which still leaves "configuration" to mean that you can be configured for landing and have a normal safe landing?!)

​​
Hahaha. I think airbus technically refers to the various positions of the high lift devices as config 1, 2 etc


But I take your point
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Old 6th Jan 2022, 14:59
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Originally Posted by CrazyStuntPilot View Post
We sent a Tech Request a while ago and this is what Airbus said about this topic (320 family; there are other reasons to select gear down as per SOP on, say the 350, e.g., for the PLT to finish before landing):
Thanks. This is exactly what I was looking for. I'll note 2 things though:

1. The response concludes with them saying there's no technical objection. I take that to mean the hydraulics aren't an issue.
2. I'm not aware of any US airline that will allow you to continue a landing if you're not fully configured by 1000ft, so the 750ft point is moot

That said, you(pl) were right, and it seems Airbus wants it to be a 2 step process. I'll do my best to remember that on my next trip.

My learning continues.
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Old 6th Jan 2022, 15:24
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Originally Posted by Check Airman View Post
2. I'm not aware of any US airline that will allow you to continue a landing if you're not fully configured by 1000ft, so the 750ft point is moot
Even for visual approaches??
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Old 6th Jan 2022, 16:06
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Originally Posted by pineteam View Post
Even for visual approaches??
Even for visuals. You can be a bit fast at 1000, but if you're not fully configured by 1000, automatic GA.

(and no, you can't cheat and reconfigure for a flaps 3 instead of full at 980ft)

What altitude do you use for visuals?

Last edited by Check Airman; 6th Jan 2022 at 16:25.
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