A320 Unreliable Airspeed Actions

[320p]

Hello,

Memory items are to be applied if safe conduct of flight is impacted.FCOM has listed some indications which point toward application of Unreliable speed actions.They seem to be more applicable when airborne or in flt.My question relates to action to be taken once above approx 100 kts during T/O roll till above MSA or circuit altitude.Would following conditions dictate application of immediate actions-
- Loss of speed tape or speed stuck on either side?
- Loss of ADR 1 or 2 and that side PFD indications?
In short any ambiguity of speed indications on either PF or PNF side during this phase.

Thanks.

[Narrow Runway]

Hi,

A previous employer used 100 knots on the A320 as a mental cutoff point.

In essence, a reject at <100 will lead to a fairly uneventful outcome, if handled correctly.

A reject at >100 is a high speed, high energy, quick reaction time event.

I always brief:

" We will abort for anything significant up to 100 knots. Between 100 knots and V1 (of x,y,z knots) we will only abort for:

* Any fire warning, an engine failure confirmed by 2 parameters, a blocked runway or anything that leads me to believe that the aircraft cannot safely fly.

Beyond V1, nothing to be done except calling rotate and positive climb etc etc...."

I would bracket your examples as in the latter reject case if before V1.

If they occur after V1, then you are into the unreliable airspeed memory items. At this stage it is a GO call, and memory items are to be applied immediately, i.e. TOGA power and rotate to 15 degrees on the call of rotate - not before, then at thrust reduction select climb power and 10 degrees. Then, climb away to a safe altitude and consider completing any after take off checks and entering the QRH for the remainder of the unreliable airspeed drills.

Any other thoughts from fellow A320 Captains or FO's?

[Slasher]

Having once run into a bunch of birds in this thing during TO
just as gear up call was made its reasonably straight forward.
Me FO was flying and called "airspeed frozen you have control
now". After smashing into the avians I also doubted my IAS
so we just TOGA'd and 15 degree'd as per the book. Cleaned
up according to the book too but had a quick squiz at the GPS
GS which almost matched the ISIS speed.

FO's IAS was stuffed but mine wasn't all that credible either,
so decided to return by using the book attitudes/speeds/N1s
etc in concert with the ISIS IAS and GPS GS. Everything was
matching and the wind was light so we let down using ISIS
and confirming same with GPS, relieving the FO of the QRH
after the GA gen was noted (in case).

After that 757 Lima prang in 1996 I always check both ASI's
(mine and the STBY) at the 100kt call. If they don't match I'll
rip out the buckets without hesitation and stop.

Only problem is the ISIS and those older SBY ASIs in the 320
suck-squirt are really too small and piddly to read quickly and
comfortably - not to mention totally outside of the readability
vision of the FO).

[proxus]

TOGA power and rotate to 15 degrees on the call of rotate - not before

Just wondering, how do you "call rotate" when you have unreliable airspeed?

[320p]

Hi,

After airborne,actions are clear and I believe would dictate application of memory items in cases where we have even an iota of doubt and below 100 kts, a reject.

My doubt is what happens between 100 kts and V1?

Would situations like Loss of speed tape or speed stuck on either(one) side/ or Loss of ADR 1 or 2 and onside PFD indications ,dictate:
-a reject
-handing over of control!!!
-or call of unreliable speed by either pilot and application of immediate actions.

[Narrow Runway]

Unless your company uses "Wet Figures", to ensure a split on almost all occasions - or unless it's a genuine wet runway - the V1 Rotate call will be simultaneous.

Therefore, if before V1, as in my example: STOP!!!

[ironbutt57]

Look... from to PA-28 to B757 to Grumman...(F14)...pitch attitude thrust......called being a pilot...really.....:ok:

[ironbutt57]

@320P...I HOPE you stop....when did we all forget how to FLY???

[misd-agin]

Slasher - "After that 757 Lima prang in 1996 I always check both ASI's
(mine and the STBY) at the 100kt call. If they don't match I'll
rip out the buckets without hesitation and stop."



Our SOP uses 80 kts for airspeed check with 100 kts the cutoff for low vs. high energy aborts.

After verifying T.O. power is set I mentally say "speed, speed, speed" and check FO's, STBY and then my airspeed. Verifies correct airspeed while at slow speed (<80 kts).

[Slasher]

80kts in our mob is not a call - thats only the point where the
ECAM TO Inhibit starts. 100kt is used as a "end-of-low-speed
-abort-so-don't-reject-unless-its-really-serious" reference call
which also doubles as my ASI crosscheck.


My doubt is what happens between 100 kts and V1?

What NR said - stop.

If within 10 kt of V1 (esp at high speed) - don't think - TOGA
the bloody thing, rotate and fly it.

[Microburst2002]

Just wondering, how do you "call rotate" when you have unreliable airspeed?

That is a really sensible thing to wonder about!

If one speed tape fails, the othe guy has control, you may continue.
In a case like a bird strike such that you dont' trust any speed indication (and therefore speed is unreliable by definition) then can we apply V1 rule?

We can, but then when will we rotate?

[rudderrudderrat]

Hi Microburst2002,
We can, but then when will we rotate?
The IRS ground speed won't be affected by the bird strike, and you'll be aware of the surface wind component.

[Microburst2002]

Too complicated for me, specially because I would be surprised.

In 320s, VR Is scarcely one or Two knots above V1, so the v1 rule applies well. in a 380, however, things would be more complicated.

By the way, once in flight I would never rely on any GS. In a hot day with low Qnh and a strong wind component, considering GS could prove fatal.

Of course, TAS is to be disregarded sistematically.

i think that it is better to follow the procedure, fly pitch and thrust till safe altitude, then maintain altitude with target pitch with thrust as required, then trouble shoot, finding if there is a IAS consistent with the associated speed.

If no ADR is reliable, then fly as per the tables and ignore GS, specially in approach. i have seen many pilots who do not understand how ro fly a 3 degree G/S with a 4 degs pitch. Then they try to fly the ILS with reference to GS and threshold speeds are usually too high, although they land...

[rudderrudderrat]

Hi Microburst2002,
We can, but then when will we rotate?
In 320s, VR Is scarcely one or Two knots above V1, so the v1 rule applies well. How do you know you've passed your V1 or VR if you have unreliable Air Speeds?
I was simply suggesting that, in the absence of any reliable air speeds during the later stages of a continued take off, the ground speed read out would be a clue. Nothing more.

[misd-agin]

When do you rotate? You can rotate anytime you think "we're moving now!" :ok: If that doesn't work rotate prior to getting mud on your tires.

The investigators aren't going to hang you for rotating after Vr.

[reubenjosephdsouza]

Hi there just a few inputs from me and what we doin our company,

We have a company circular which states that if we have ne issues related o airspd such as the one mention of both PDF v/s Isis givin wacked readings ,capt has the option to reject the takeoff till 100 kts and provided the diff bet readings is greater than 6 knots , above100 is a regime of high speed reject and should be carefully taken into consideration, rather than being fast on rejecting its safer to continue the t.o. Following the Airbus published unr.airspd,checklist ,memory item,finishing the given checklist and carrying out a landing using Isis,gps cross check and being very careful.

But yes if it is necessary to reject considering Flt safety issues by all means reject!

Also just my question if u have ADR 1&2. Faulty we need 1 ADR for the t.o. And other system functionality to work, so how about continuing the takeoff if ur sure Nutin else is affecting Flt safety , carrying out the airbus recommended memory item and landing back?

Or could continueing
the takeoff on the only surviving ADR affect other stuff,just a thought .

[Microburst2002]

Hi, RRR

I know. I only say that for me it would be difficult to make the maths of GS VR equivalent after the surprise of having an airspeed indication problem in the middle of the take off run.

Then I just critisised use of GS in flight.

All this matter can be very complicated. I mean, the most difficult part of it is coming to the conclusion that speed is unreliable. If only one speed tape gives a red flag, then the other pilot should continue and after take off, his AP should be used. There is a reliable speed.

In the case of bird strike such that you don't rely on any indication, if the strike occurs before v1, RTO. If it occurs after V1, in the 320 rotate shortly afterwards. In bigger airplanes, I don't know, maybe continue rolling and rotate before max tyre GS?

[TyroPicard]

Don't forget that all ADR cautions are inhibited above 80 kts.......

[Slasher]

In bigger airplanes, I don't know, maybe continue rolling and
rotate before max tyre GS?

From memory - in Boeings, in windshear, it said to initiate a
gradual rotation within the last 2,000ft of remaining runway.
If you can't read yer Vr in the 320 (esp if heavy) I'd borrow
that and do the same. Who cares if you're a few knots above
V2? If you were to lose a donk on top of your troubles, you're
already at TOGA, and a few knots above V2 acts in your favor
anyway.

[javierito]

Hi 320p,

You must think in only one item when considering speed problems between 100 kts and...supposely V1. Can the aircraft fly in asafe way? Are you able to land it again in a safe way?
The answer is a captain decision only, first officers can only wish the captain has a good day,
If the answer is yes, then it is better to fly it.
If the answer is no, it is better to stay on ground.

From my humble point of view, two speeds going wrong is enough to stop the aircraft on ground as no safe landing can be assured if airborne.

[Microburst2002]

Landing without airspeed indication is piece of cake.

[Slasher]

Oh in the sim its an absolute piece of piss.

Try doing it for real in China on a dark and stormy night! :uhoh:

[misd-agin]

Low altitude is much easier to deal with vs. dealing with it at high altitude.

[Natstrackalpha]

Narrow (I think I can guess who you fly for by your T/O brief)

Why have you all missed the standby airspeed indicator? Why did you bug this before departure in the first place?

Why is there a V1? Therefore why, if indeed this is the case, do you want to continue boyond V1 if a fault dictates (as per yer SOPs[maybe]) that you would reject <V1 in the event of . . .?
Why not scrape the rubber and burn the paint off and stop?
If continuing (as you are the Captain) then back to my first question, the standby airspeed indicator - thats what it is there for. Will, the FMGS airspeed calcs still give accurate enroute ETAs etc., etc? I mean, will you still get there?

Also, and with prescence of mind presently flying a coffee cup on my desk, why brief `this` and then go and do `that`?
Surely, if you have said, either of us can call stop <V1 for this and that, does that part of the pre-departure brief include Unreliable Airspeed Indication? I think not.
Which gives this thread much validation and value. Ton pied.
But if it does (which is does not) then surely the answer is to stop and vacate.

My point? Unless not otherwise stipulated (in the brief) why be creative?

Or, in the words of Narrow: STOP!!!

[Airmen25]

Im new and under training. In my company, at 100kts PNF will call out "100KTS" for a speed check with the PF. Therefore, in this situation on the T/O roll with one of us having an unreliable airspeed or if both PFD speeds are not sync, below V1, we would stop. In my humble opinion, i totally agree with this policy of my company because i don't see any good reason to get off the ground with such an abnormal situation prior to V1, let alone, V1 has been calculated to provide you with sufficient distance to abort the T/O. Also, like Slasher said, it ain't so easy no more in a dark night with poor weather conditions if you decided to continue. But, thats just my opinion.

[Microburst2002]

very true.

The problem is if you have red flags after that.

The problem of Unreliable speed is that it is Unreliable. You don't know which speed is good. STBY ASI is as unreliable as any other speed indication.

From the moment you come to the conclusion that speed is Unreliable (which is the most difficult thing) then you trust no indication at all and manually fly pitch and thrust or pitch and flight path, depending on the circumstances.

If it happens at high speed in the middle of the take of run, well, it is a tricky situation which has not been foreseen in the procedure. What if you STOP and it happens that actual speed is very high and it is long time you passed V1? Then you will overrun the runway, that's what will happen. What if you continue? At what speed do you rotate?

there is no way to make a 100% safe decision. Probably in this case pilot instinct will make the decision. If the pilot feels that he can stop within remaining runway, he will stop. It he feels he will not, he will continue and rotate when he feels he can. And then apply the procedure

[Airmen25]

Thanks alot Microburst2002, it make sense too, i guess its pilot judgement as well.