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Display Unit failure during rotation

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Display Unit failure during rotation

Old 26th Mar 2022, 06:19
  #1 (permalink)  
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Display Unit failure during rotation

Hello everyone,

I have a question about a scenario that was recently applied by my fleet for a recurrent test (777) but I think applies to most fleets.

The scenario is during takeoff after 80kts but before V1, the FO side PFD and ND both fail.

My question is do you reject takeoff or not?

According to 777 QRH Maneuver Section on RTO: If below 80kts would probably reject due to this falling under the category of “system failure(s)”

But above 80kts this failure technically doesn’t fall under any RTO criteria except for “airplane is unsafe to fly”

So I guess depends if you think this failure constitutes “unsafe”?

Also suppose I did takeoff with this failure, would I also be legal to continue to my destination (although not encouraged)?

The requirements for 2 PFD and 2 NDs are supposedly for planning stage (required equipment at dispatch).

Any insight or discussions about this is much appreciated thanks!

KG21
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Old 26th Mar 2022, 07:31
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GO.

GO!!

Remember, any time something happens in the high speed RTO regime, you don’t have time to diagnose. With the exception of the items listed in your briefing to STOP, most other malfunctions are far more likely to compromise your STOP capability than your GO capability.

I’m not familiar with the 777 however on most types, the simultaneous loss off two screens is not going to be a coincidence. Odds are the screens are fine, but you’ve lost the associated SG or both have no power, which means a bus failure.

but you still have 2 sets of instruments and two engines, so it is perfectly safe to take off.

Once safely airborne, figure out root cause (even money says you’ll find other stuff is unpowered off the number 2 busses, or the SGU is screwed. Run the appropriate NNCs and then TDODAR (or whatever your company decision making tool is). The continue or return decision is going to be situational.

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Old 26th Mar 2022, 08:48
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In the high speed regime I would not expect you to stop for partial loss of displays.

Perfectly safe to takeoff.
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Old 26th Mar 2022, 10:08
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Wasn't there a Boeing notice in the 744 handbook for a situation where ALL the DUs could fail at exactly the same time due to EIU issues, subsequently fixed by a change in EIU spec? Fixed temporarily by recycling EIU CBs x 3?
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Old 26th Mar 2022, 10:25
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Definitely GO.
I never operated B777 but on the closely related B744, only reject after 80Kts for the "big 4"
The big 4 -
Eng Fail
Eng Fire
Predictive Windshear
Capt believes the the aircraft can't fly
Should this failure mode - no PFD or ND F/O side - occur, you still have both Capt displays, lwr EICAS screen avbl as ND and ISFD for attitude etc.
Once in the air with safe flight path assured, then run appropriate checklists and decide your next move.
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Old 26th Mar 2022, 14:31
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Another subtle consideration not touched on yet, is without their PFD, if the affected pilot is the PM, how are the v1 and rotate calls going to be conducted. The pilot flying will largely looking outside and likely be unaware of the failure affecting the other side and waiting for the usual calls. How does the PM communicate clearly the failure and the requirement for the PF to call/monitor the speeds for themselves. Or can the PM clearly see the other screen on a 777. Startle factor could also of course come into play. Sure sounds straight forward enough here on the ground to communicate the problem, but going down the runway at speed not so easy.

if the affected pilot is PF and it happens just before or during rotation, chances are neither pilot is going to notice 2 screens have failed until already airborne and climbing away. The PF at some point is going to have to hand over control. The urgency of this to happen I imagine depends on most likely the cloud base or visibility.

below 80kts, without the second screen how are you going to cross check the airspeed indications, so stopping should occur either way in that scenario.

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Old 26th Mar 2022, 15:31
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Standby instruments, or ISFD, are the fallback but are only of use if you can remember, or have written down, the relevant speeds. Sad day when the Accountant removed the little paper bug cards from the Inventory.

Anyone here every actually had to fly on Stby instruments for real? Just curious. Only ever lost all 6 DUs in the Sim, twice.

KG21. What was your company opinion of that scenario?
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Old 26th Mar 2022, 16:35
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Our company has an airspeed check at 100kts (A320), if it was before that I would still abort. The scenario doesn't specify who is the pilot flying but the way it is phrased I assume LP is PF. How is the PM supposed to call V1/Vr with no screens? And if the RP was PF, it is probably worse, how is he supposed to fly without instruments ("your controls, my screens are dead" during rotation would definitely cause a distraction...)? A consideration I have with electrical issues like this is that they sometimes grow worse. I know we are all trained to be go oriented in the high speed regime, but I am not sure if this is always simple GO call even though I would elect to continue on a "short" runway.
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Old 26th Mar 2022, 21:07
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If you reject for any failure other than the ones listed as mandating a RTO above 80, you will have done the wrong thing. That's it at a first glance. However, there's a catch. What failures make the aircraft "unsafe or unable to fly", as the last point on the list suggests? I'm not aware of any exhaustive list of those. Hence, it's ultimately down to PIC judgement.
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Old 26th Mar 2022, 21:18
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Anyone here every actually had to fly on Stby instruments for real?
Yes thank you. I’m not alone in this as many others flying C560XL, Citation X, Dornier 328 have experienced the cascade failure of early low mod state Collins screens. Flying an approach to minima using a SFD such as a Meggitt should be expected of a pilot.

All this talk from magenta-line generation about lack of speed info; do you not know the expected attitudes to aim for? And as for this ‘startle factor’ and ‘no one will notice until airborne’, or how to communicate a screen failure … Are you not trained to always expect the unexpected, monitoring pilot to monitor, and how to communicate a failure?

What has become of the professional pilot and basic airmanship?
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Old 27th Mar 2022, 00:49
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A320 Left seat

A very interesting question, here is my take.

As stated earlier, up to 100kts on the A320 is considered "low speed" for a RTO. (It was 80kts from memory on the 787)

On take off, I attempt to quickly scan left to right across the cockpit as we approach the "100kt" call, this takes in My PFD/ND, ISIS, EWD, RH PFD/ND. My theory is I will be aware of any issues with Airspeed discrepancies, failures etc prior to the "High Speed Regime" starting. (this is made more difficult in high crosswind, 30m Rwy or LVP conditions)

Hopefully if I was faced with this failure, I would have enough SA to either STOP or GO in a timely fashion regardless of whether I was PF or PM.

If the F/O is PF, the startle factor and the ability to get a clear message out will be the hardest part.

But that's what we get paid the big bucks for.
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Old 27th Mar 2022, 01:09
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Originally Posted by V_2 View Post
Another subtle consideration not touched on yet, is without their PFD, if the affected pilot is the PM, how are the v1 and rotate calls going to be conducted. The pilot flying will largely looking outside and likely be unaware of the failure affecting the other side and waiting for the usual calls. How does the PM communicate clearly the failure and the requirement for the PF to call/monitor the speeds for themselves. Or can the PM clearly see the other screen on a 777. Startle factor could also of course come into play. Sure sounds straight forward enough here on the ground to communicate the problem, but going down the runway at speed not so easy.

if the affected pilot is PF and it happens just before or during rotation, chances are neither pilot is going to notice 2 screens have failed until already airborne and climbing away. The PF at some point is going to have to hand over control. The urgency of this to happen I imagine depends on most likely the cloud base or visibility.

below 80kts, without the second screen how are you going to cross check the airspeed indications, so stopping should occur either way in that scenario.

Keep going



Doesn’t the 777 automatically call out V1 ? not a big deal even if it doesn’t the Pilot whose displays are operating can glance down and determine if VR has been reached
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Old 27th Mar 2022, 06:49
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320 trained. Go. Our cut-off is 100 kt, however.

No contest, no justification, no need to stop. As much as I dislike the ad-extremis emphasis on not attempting to stop, more so when 100 kts are achieved still inside the THR-side touch-down markings.

How did we get to the point where stopping safely is a sin would be a different discussion.

EDIT: Hope it is not wrong to assume the PIC eye-focus for the high-speed part is 50% engine, 25% ASI, 25% outside

Last edited by FlightDetent; 27th Mar 2022 at 08:38.
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Old 27th Mar 2022, 08:01
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Originally Posted by hans brinker View Post
Our company has an airspeed check at 100kts (A320), if it was before that I would still abort. The scenario doesn't specify who is the pilot flying but the way it is phrased I assume LP is PF. How is the PM supposed to call V1/Vr with no screens? And if the RP was PF, it is probably worse, how is he supposed to fly without instruments ("your controls, my screens are dead" during rotation would definitely cause a distraction...)? A consideration I have with electrical issues like this is that they sometimes grow worse. I know we are all trained to be go oriented in the high speed regime, but I am not sure if this is always simple GO call even though I would elect to continue on a "short" runway.
Being go minded is mind set to have as you move closer to V1 but well short of V1 if not sure nothing wrong in stopping. It could get complicated if engine failed near V1.
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Old 27th Mar 2022, 13:19
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Originally Posted by blue up View Post
Standby instruments, or ISFD, are the fallback but are only of use if you can remember, or have written down, the relevant speeds. Sad day when the Accountant removed the little paper bug cards from the Inventory.

Anyone here every actually had to fly on Stby instruments for real? Just curious. Only ever lost all 6 DUs in the Sim, twice.

KG21. What was your company opinion of that scenario?
Thank you all for the replies!

Our scenario was FO is PF and both of his DU’s failed above 80kts but below V1.

Some IP’s I’ve heard were more oriented toward stopping even close to V1 so I guess that’s what confused me.

Like you guys said, nothing is cut and dry, but the basic premise of consider to GO when closer to V1 I think is a good start.
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Old 27th Mar 2022, 13:21
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Surely if PM loses their screens they'll just look across and call V1 and rotate off PF's? Or am I missing something here?
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Old 27th Mar 2022, 15:04
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Surely if the F/O does not call V1+r ...
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Old 27th Mar 2022, 19:00
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My employer gave us a fascinating brief and training on takeofff decision making on the A320. The example was EEC in the high speed regime on the 320 which obviously leaves only CAPT PFD/ND and the upper DU.

On a short runway rejecting for this (the warning for which is which is inhibited above 100kts) leads to a runway overrun due to the loss of a large number of stopping devices. The emphasis was Airbus have done the thinking for you in the ECAM and inhibit design, and to trust it. Certainly I (current Airbus captain) wouldn’t consider loss of one side’s displays as “malfunctions or conditions that give unambiguous indications the aircraft will not fly safely” - in this case I think the Airbus FCTM wording makes the point about what you should be considering much better than the Boeing.

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Old 27th Mar 2022, 19:16
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Originally Posted by Fursty Ferret View Post
Surely if PM loses their screens they'll just look across and call V1 and rotate off PF's? Or am I missing something here?
I thought it would have been an obvious solution. Not sure how the 777 is set up with the yoke in terms of visibility, but the visibility on the Airbii is quite sufficient for either pilot to read the offside PFD.
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Old 27th Mar 2022, 20:24
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It’s an indication functionality, not a unsafe aircraft. Look on the MCP, there’s your V2. Use it as a rotation speed, or use runway lights. It will fly safely, don’t worry. Why would you want to reject a perfectly safe aircraft with double indications available (stand-by and PF side)?

Btw, I believe on the 777 the PFD display will automativally transfer to another display.
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