Vilnius crash

• Tuesday at 8:58 PM

• #2

LittleInch

Petroleum

Mar 27, 2013

22,384

How did it crash if the A hyd pumps are still on?

 

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• Tuesday at 9:42 PM

• #3

TugboatEng

Marine/Ocean

Nov 1, 2015

11,774

The leading edge slats retract when the B hydraulic pumps are turned off. The flaps were not extended. The plane stalled.

 

Last edited: Yesterday at 12:05 AM

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• Tuesday at 11:14 PM

• #4

G

Garbage1

Civil/Environmental

Oct 31, 2024

152

 

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• Yesterday at 8:30 AM

• #5

LittleInch

Petroleum

Mar 27, 2013

22,384

So a and b are two separate systems which don't inter connect? That's not intuitive.

From the excellent b737 site http://www.b737.org.uk/hydraulics.htm

There are some automatic and manual cross connection between the two systems, but it looks rather complex all right.

 

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• Yesterday at 9:13 AM

• #6

M

MintJulep

Mechanical

Jun 12, 2003

10,080

In the moments before they were switched off there were calls for the engine anti ice to be used. This strongly suggests that the hydraulic pumps were mistakenly switched off instead of the engine anti ice switches.

Click to expand...

I don't follow.

Up is off, down is on for both sets of switches.

I'd guess that convention is applied for all switches.

If so, I'd expect that to be ingrained. How do you mistakenly turn a system off when you're intending to turn something on.

 

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• Yesterday at 10:29 AM

• #7

LittleInch

Petroleum

Mar 27, 2013

22,384

I guess he just thought to move them to a different position than they were to start with....

There are a whole bunch of very similar switches and some will normally be on and others off.

It is a pretty big error, but the fact that only kne hydraulic system runs the flaps is a bit single point failure and it would seem there is no feedback that the flaps weren't moving when commanded?

 

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• Yesterday at 10:42 AM

• #8

M

MintJulep

Mechanical

Jun 12, 2003

10,080

If we believe your earlier link, then I don't see any hydraulic backup for TE flaps.

I guess the mitigation is "you'll be landing fast, deal with it."

From the excellent b737 site http://www.b737.org.uk/hydraulics.htm

 

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• Yesterday at 11:05 AM

• #9

LittleInch

Petroleum

Mar 27, 2013

22,384

That seems to be the case. There are some cross over elements, but the "power transfer unit" seems toexostfor the LE flaps only. It's not clear if its on,y to retract them or extend them, but the TEflaps are system B only by the look of it.

Apparently that rrrr rrrr rrrr noise you sometimes hear after landing when they are retracting the flaps is that PTU working when they've only one engine or one is at idle. Apparently.

 

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• Yesterday at 11:31 AM

• Thread starter
• #10

Alistair_Heaton

Mechanical

Nov 4, 2018

9,744

Now go have a look at the MAX and see if the same situation exists

 

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• Yesterday at 12:37 PM

• #11

LittleInch

Petroleum

Mar 27, 2013

22,384

From what I can see the hydraulic system for the MAX is basically unchanged from the NG.

So you really don't want to lose your no 2 engine by the look of it.... There is an electric pump but it is lower capacity.

There are some elements of standby and crossover, but I think to would take you a good few minutes to work it out and the standby / third system is pretty low of fluid power. I don't think anything other than system B runs the trailing edge flaps.

 

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• Yesterday at 3:46 PM

• Thread starter
• #12

Alistair_Heaton

Mechanical

Nov 4, 2018

9,744

I would be amazed if it's changed since the original 737 from the 60's

If it had it would have triggered a requirement for a different type rating.

The NG manage to escape a raft of certification changes by a matter of weeks. And if the system hasn't been touched then it will be the same on the max.

Surprised there isn't guards over the hydraulic switches. I am pretty sure the hydraulic kill buttons had them on the Jetstream and the Q400.

 

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• Yesterday at 5:03 PM

• #13

TugboatEng

Marine/Ocean

Nov 1, 2015

11,774

You know what they say, doubling redundancy doubles the chance of a failure.

 

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• Yesterday at 6:18 PM

• #14

IRstuff

Aerospace

Jun 3, 2002

44,689

it would seem there is no feedback that the flaps weren't moving when commanded?

Click to expand...

The flap position was recorded in the FDR, so that reflects some indicator in the cockpit, which the pilot(s) apparently didn't check, particularly when specifically asked about it.

 

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• Yesterday at 6:28 PM

• Thread starter
• #15

Alistair_Heaton

Mechanical

Nov 4, 2018

9,744

I seem to remember it's a not very noticeable 1" diameter dial next to the gear handle.

The A220 flap/slat indication also isn't very in your face. Not that it really needs to be as the flap selector handle is easily seen. And if it's not at the selected position it triggers a master caution and tells you.

 

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