Landing gear malfunctions

[John H Watson]

The AMM has a chapter for taxying and towing. It restricts the MAC to 24% when towing an aircraft with only the wing and nose gear extended.

Regards
JHW

[Hardy Heinlin]

24%. Thanks, that helps! I can set this restriction. Perhaps 0.5% more for safety.

[Hardy Heinlin]

Looking at the people, I'd say about waist height. The belly is flat in that area.

3 ft?

My other factor is the pitch angle for the sine. I'm using 7° nose down. Perhaps it's a bit too much. I didn't measure this with a microscope because I consider such a scenario a chaotic one with dirt, scratches, damages etc. The model doesn't sit on a glass table.


Cheers,

|-|ardy

[Hardy Heinlin]

Current Alpha status:








(Click on pic to get 1920 x 1200)


|-|

[Hardy Heinlin]

Found my mistake: My RA antennas were almost at the nose gear :-)

After the correction I'm now getting with nose tip down -10 (200 tons) and -12 (400 tons). With all gear up it's -14.


|-|

[dutch57]

Hardy, goodevening

The Ra altutude read outs are fine in your last post.

When dispatch load an aircraft , they aim for a mac between 21% and 28% , if a plane has a mac of 41% tailtipping may occur , KLM has the limit set at 38% cg alarm during loading/unloading.
If a plane lands with predicted mac of 36% , crew radio`s ground to inform them for special unloading procedures with a combi we place tail-jack, or first unload pallets at the main deck, before unloading the pax.

If a plane under normal mac limits you do nor have to worry about weights on the gears it will be sufficient to perform taxi operations as descriped in the FCOM.

If you check the ECL for unsymetric gear operation you can see the limitations, if both body`s are retracted or both wings are retracted.

sincerly,
Bob

[Holger Wende]

Hi,

does the flight path vector symbol remain visible when ground speed is zero (and neglectable winds), ref. #24?

I just wonder because the Air France accident reports state that in Airbus certain attitude information is removed when expected to be unreliable. But with zero ground speed (and presumably low winds) the FPV is "unreliable", isn't it?

Regards, Holger

[Hardy Heinlin]

Hi Holger,

good question. I'm not sure. What I've learned is that the IRS lateral track value reads zero below 80 knots groundspeed, i.e. already at 80 (not only at 0) knots the track display is of no use anyway. I assume the vertical track is then neutralized as well. So, it could be that the entire FPV should be removed below 80 knots. But the track lines on the compass roses remain displayed. I believe the FPV remains enabled, too. This way you can at any time test if the FPV button works.


Cheers,

|-|ardy

[Hardy Heinlin]

I forgot to remember: The FPV is visible on many photos of parking 744 aircraft.

[Will]

Hilarious pictures!  Have you tried taxying around with only the wing gear extended?  Could you use brakes and engines to keep the plane balanced?  Hours of fun!

[Hardy Heinlin]

It's impossible to keep it balanced. The CG lies higher than the pivot, so the attitude is unstable. Before you notice any trend, it's too late to spool up the engine :-)

There's also an unpredictable unsteady friction coefficient for the metal-asphalt contact. Sometimes there's an ant in between, or a lost shoe (probably from the airport director).

[Will]

So how about retracting the nose gear only, and taxying around on the wing and body gear?  That should work...

[Hardy Heinlin]

With 5 individually retractable gear groups, I've counted ca. 18 different constellations affecting the ground attitude ...

[Will]

In both pictures you posted, there's a tiny diagonal red line extending a few pixels out from the lower edge of the ALT GEAR EXTEND NOSE/BODY button.  What is the line?

[Hardy Heinlin]

Copper wire.

[Will]

And it's not on the WING button too?

[Hardy Heinlin]

If you put it on the WING button, too, then it's on that one, too. There's a little hole in the cover.

The wire is for protection. You need an extra mouse click to tear it off. Then you can open the cover. And then you can push the button.

[torrence]

I assume the original intent behind guarded/wired switches is 'idiot-proof, double protection' for a function that might become necessary or critical but that the gods behind the machine really, really don't want punched accidentally or without at least some thought.

I think Hardy is using these things so much in testing he's forgetting to re-wire before each flight

Cheers,
Torrence

[Will]

Sorry to be obsessive over details, but then again I'm sure you appreciate that... :-)  So BOTH switches can be wired shut, I'm guessing that in these pictures, the copper wire been broken for the WING switch, but remains still in place for the NOSE/BODY button?  Got it.