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Checklist Challenge and Response theory.

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Checklist Challenge and Response theory.

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Old 20th Oct 2002, 14:17
  #1 (permalink)  
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Checklist Challenge and Response theory.

Boeing 737 advice on challenge and response infers (for example) that PNF reads "Landing Gear". And PF checks visually for lights and lever and responds "Down and Three Greens"

Or another one. On final PF calls for landing flap. When action is completed, the PNF calls one word "Flaps" - and waits for the response -which may be "Thirty Green Light.

This policy correctly forces the responder to physically check the position and indication before responding. If the response is wrong - then the PNF picks him up and action is taken to correct the problem.

If, however, the policy is changed to the PNF reading the challenge and also giving the response before the PF gives his response, then the challenge and response theory is compromised, because it is possible for the PF to parrot back the response given by the PNF without checking.

Can anyone offer advice therefore, on why, in a Non-Normal checklist where Boeing advocate that the PNF both challenges and responds to a switch or lever position, the landing check (for instance) of Gear Down and Three Greens, is challenged AND responded by the PNF as well as responded again by the PF.

Is this not only a checklist overkill, but also a misinterpretation of the Boeing intent - which by the design of the Normal Procedures philosophy, requires an independant non-prompted response by the PF?

In other words, why in the 737 Non-Normal landing checklist does the PNF put words into the mouth of the PF by announcing the what the response should be? Or have I got it all wrong?
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Old 20th Oct 2002, 15:38
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One theory which is subscribed to by several companies (including my own) is that once the aircraft is in motion the handling pilot (PF) should not be distracted by having to take his eyes off whatever he's doing and that the PNF is quite capable of checking that an action has been carried out.

There is, of course, a danger that the PNF will simply "sing out" the expected response, and that both pilots should be checking and cross-checking each other.

The use of challenge and response is, IMO, a valid one, and I disagree with my company's method of operation. However, they pay me, so until they change the SOP I shall do what they ask of me.
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Old 21st Oct 2002, 00:22
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I have over the years used just about every system there is, and they all have pitfalls and good points. - The challenge and response can generate a motor-programme response without checking, and the 'read and do' is basically un-monitored. We are sometimes more task-oriented than result-oriented in this business IMHO, ie. checklist completion is the goal, not what the checklist does. I guess in the end it is always down to individual discipline, if that is assured so is the result.
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Old 21st Oct 2002, 03:22
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I guess the main distinction will be the operation during normal and non-normal procedures. Remember during non-normal situations, both PF and PNF have very distintive duties. Generally, PF is concerned on getting the aircarft down safely while the PNF provides all the support.
Thus it would seem that Mr Boeing feels that during high stress situations the PF should not be distracted and the PNF takes on more duties.
Well thats my opinion anyways...
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Old 22nd Oct 2002, 13:27
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Yes - I understand the probable reason behind the Boeing philosophy of the PNF reading and answering at same time as well as the PF responding to Non Normals. But we never really know the real thinking behind it because Boeing won't tell us.

My question (rather badly put in retrospect) concerns the landing gear and flap challenge and response difference between the Normal and Non Normal landing checklist.

Talking to some old and bolds of the early B727 and 737-200 era, the policy by Boeing as interpreted then was for the Non Normal Landing checklist challenge to be the same as a Normal Landing checklist. That is: PNF calls Gear.....PF replies Down three greens. PNF calls Flaps......PF responds Fifteen Green light. Or whatever.

Somewhere along the way I believe the Boeing philosophy has been corrupted/misunderstood/improved? Who knows? Personally I am happy to call out Gear and get a single response
of Down Three Greens from the PF.

Same point on configuring by the first officer from a Bleeds on to a Bleeds off take off and vice-verce. Years ago this was a simple straightforward task completed in a few seconds without fanfare by a competent person. Normal "C" or "reverse C". The captain cocks an eye in that direction and Bob's your Uncle - job done.

Now the whole bleeds selection process smacks of massive precautionary overkill with the RH seat pilot carefully placing his fingers on one switch at a time while singing out a nervous query of "Confirm?" While the other pilot looks across and hollers "Confirmed". Repeat for all other switch selections. Meanwhile for a short time while all this cross-confirming is taking place it may be that no one is looking where the aeroplane is flying. I mean to say - is all this really necessary when it wasn't required all those years ago?
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Old 24th Oct 2002, 12:47
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Hi all,
No it's not, Centaurus, you just pre-brief the Flight Engineer to have what is required done at the appropriate moment, and it gets done, simple eh!

The 3 crew system works very well, the FO reads the normal c/list whilst the acft is stationary, and the FE reads ALL c/lists when the show is moving!
When a non-normal is being read, the FO flies the acft, and the Capt and the FE complete the necessary c/list, and, during engine fire shutdowns and suchlike, the FE and the PNF confirm each other for the initial actions, then the Capt and FE system restarts!

It all works very well, Cheers
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Old 28th Oct 2002, 16:37
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Earthmover is right on !
The idea is to accomplish the task, not see how fast we can get through reading the checklist. There is no rush! this is what has caused several accidents in the past.

Think back to single pilot operation, do we read the response verbatim, just to say we did the checklist, or do we make sure the item is infact done?
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