A330 Unreliable Airspeed Indication/ADR check proc..

[albertofdz]

Good evening to all:

Having been reviewing this procedure, and related info from the FCTM, I have come across a slight doubt.

According to QRH,specifically, the "LANDING GEAR DOWN IN LEVEL FLIGHT" chart, found in the "INITIAL AND INTERMEDIATE APPROACH AT LEVEL FLIGHT" section, states that "(EXPECT GRAVITY GEAR EXTENSION)"......

Would I be correct by assuming that this would be true only if ADR 1 and/or 3 where to "read" 280kts or more? Or would there be any other scenario where I could expect such a thing? (Say all other systems are fine of course).

Unfortunately I have not been able to test different scenarios at different speeds for this procedure....

Cheers, and happy landigs to all :)

[albertofdz]

Any ideas...??

[DutchOne]

According to the FCOM the LG GRAV EXT is only in the case when ALL ADRs are switched off (= for BUSS). If one of the ADRs is still working there is no need for the GRAV EXT.

That is because the safety valve opens if:
- lever is selected down
- speed is less then 280 kts

The speed is provided by ADR1 or 3 for system 1, and ADR2 or 3 for system 2.

So I guess if all ADRs are switched of there is no speed information to give a speed of less than 280kts, hence the valve is maintained closed.

Hope this might help.

P.s: there is a schematic in the FCOM. Check it carefully and lots of info is given.

[albertofdz]

Thank you for your reply Dutch One...

I was wondering of there was any OTHER case were the landing gear might have to be extended by gravity. As I wrote in my initial post, I fully understand the effects of having ADR 1 and/or 3 giving erroneous readings, or if they are switched off.

(btw, we don´t have BUSS installed on our A330, therefor in THIS case, unlike ADR 1+2+3 Fault, we never switch all 3 ADRs off, one will always remain on in order to benefit from stall warnings).

Anyway, once again, many thanks for your input!

[DutchOne]

According to QRH,specifically, the "LANDING GEAR DOWN IN LEVEL FLIGHT" chart, found in the "INITIAL AND INTERMEDIATE APPROACH AT LEVEL FLIGHT" section, states that "(EXPECT GRAVITY GEAR EXTENSION)"......

Could you give me the precise reference. I cant seem to find it in my books. If I have it i will check.

Regards

[albertofdz]

QRH page 34.01D.


"INITIAL AND INTERMEDIATE APPROACH IN LEVEL FLIGHT
The approach phase between Green Dot speed (clean configuration) and the landing configuration
(CONF 3), is flown in level flight.
LANDING GEAR UP IN LEVEL FLIGHT
Above 190 t 190 t - 160 t Below 160 t
CONF Speed (kts)
Pitch (°) / Thrust (% N1)
0 G-DOT 5.0 / 55.3 5.5 / 51.3 5.0 / 47.5
1 S 9.0 / 57.6 9.0 / 53.0 9.0 / 48.5
1 + F (1) S 6.0 / 59.3 6.0 / 54.6 6.0 / 49.9
2 F 6.0 / 60.6 6.0 / 55.8 6.0 / 51.1
LANDING GEAR DOWN IN LEVEL FLIGHT
(EXPECT GRVTY EXTENSION)
3 F 6.5 / 65.9 6.5 / 61.0 6.5 / 55.8"

[RoyHudd]

For approx speed for gear lowering, use GS from GPS1/2. (Unless you are operating a non-GPS equipped A330. (Scary)

[DutchOne]

Hey Albertofdz,

For this concerning procedure there is no other reason besides the faulty ADRs, as all other systems work normally (besides those effected by the faulty ADRs).

But other reasons for gravity extension could be Green HYD failure/leakage, LGCIU 1+2 failures, EMER ELEC config, locking sysem failures ect ect.

Hope this will help.

regards

[albertofdz]

Hey guys,

Thanks for your help! It all comes down to the ADR´s then, so the answer is no! In this case there seems to be no other reason :D

Cheers.

[Microburst2002]

It is a "expect". I may happen or not, depending on the ADR outputs. It is good they write that, so that if it happens you don't get caught by surprise in a very busy moment.