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In a fighter aircraft, if the checklist says turn on the radar then turn on the Heads Down Display, and the pilot turns on the HDD first would he be reprimanded for that if it makes no difference?

Is there any leeway in checklist order or are you expected to follow it to the letter? Does it just depend on the organization?

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    $\begingroup$ Checklists are developed to ensure that all the steps required for a particular activity are completed, and in the right order. If you start jumping around the checklist then sooner or later you'll miss something, and the most likely time for that is in an emergency when you absolutely must get it right. Develop good habits all the time, not just when it suits. $\endgroup$ – CatchAsCatchCan Dec 7 '20 at 21:35
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    $\begingroup$ We have some related questions that might have some useful information: here, here, here. $\endgroup$ – Pondlife Dec 7 '20 at 23:21
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    $\begingroup$ How can you be sure it makes no difference? $\endgroup$ – jcaron Dec 9 '20 at 0:05
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    $\begingroup$ Just follow the blessed checklist already, that's what it's there for. It's not a check set, it's a check list. When I get into a sailplane, it's CB SIFT CB, even if it hasn't got F=flaps, because the next one might have. $\endgroup$ – Neil_UK Dec 9 '20 at 14:24
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    $\begingroup$ You can be sure it makes no difference by knowing your aircraft systems. And he isn't asking for advice on his personal use of checklists, he is asking specifically about consequences for a military fighter pilot deviating. We all concede that following them is a good idea... $\endgroup$ – Michael Hall Dec 9 '20 at 15:57
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There is some good advice on proper checklist usage in the answers given. Like FAA and civilian aircraft manufacturers, the military preaches disciplined and proper usage of checklists.

For the sake of thoughtful discussion, I am going to take a different angle on this and answer NO to the question of the pilot being reprimanded. Read on for explanation...)

There are actually several questions here, and multiple layers to each: e.g.

  1. Is it an emergency, or not?
  2. Is it a simulator checkride, or a flight?
  3. Is the deviation habitual, (i.e. something the pilot has rationalized to self and does regularly) or a one-time mistake?
  4. And what do you mean by “reprimand”?

First, in an emergency the pilot may deviate from any procedure to the extent required to deal with the emergency. In fact, complex scenarios involving multiple system failures are regularly encountered during simulator events to emphasize the importance of sound systems knowledge and ability to run multiple checklists, which may entail performing operations out of order.

Next, detectability. As mentioned, during a simulator checkride is it highly likely that checklists may need to be combined and/or run out of order during compound emergencies. It is also expected that during a busy situation some mistakes may be made, and that the evaluator will be aware of any deviation. However, during normal operations nobody will ever know. A majority of fighters are single seat, and the ones that aren’t are typically tandem, so nobody is actually watching the pilot as they run their checklists once initial in-type flight training is complete.

Next, intent. As mentioned above, a one-time, accidental deviation that has no consequences will go unnoticed, and a mistake may be forgiven, so I will assume from your question that the pilot has made a conscious decision to regularly perform a certain operation out of order. Also, that someone else – somehow - becomes aware of it and challenges the pilot on the practice. Even this has multiple layers though because some checklists are more important than others. For example, in the pre-electrical power checklist you are just sweeping the cockpit to make sure switches are in the right place. If the pilot tells the examiner that they flip one out of order because they are left handed, the flow makes more sense, etc. the examiner will probably just let it go. However, a deviation from a “major checklist” like the landing checklist would definitely generate some discussion, which leads us to...

Reprimand. Despite the perceptions of many who haven’t served, the military isn’t quite as rigid as it might seem. Aircraft type communities “own” their operating manuals and checklists, and treat them as living, working documents. There is generally an open safety culture that encourages communication and continuous improvement via the submission of change requests. If the pilot had a valid and articulate reason for their particular personal technique they might be encouraged to submit it to the model manager for consideration. However, until the change is approved they would be corrected by the check airman, and expected to comply. Ongoing willful non-compliance would likely be punished.

Therefore, given the condition that “it makes no difference”, my general answer is NO, a fighter pilot will NOT be reprimanded for performing a step out of order. However, he/she will be expected to comply with normal procedures and demonstrate proper checklist usage during any kind training or evaluation flight or simulator.

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    $\begingroup$ I'd just like to point out that, as a career (albeit retired) military aviator, and at one time a NATOPS officer, and in multiple squadrons a standardization pilot, this is the most correct answer. Well done. +1. All of the other answer have value, as they all point out that checklists and the orders of the steps are arrived at for good and sufficient reasons in the vast majority of cases. Now and again, however, one discovers in actual service that an intially developed checklist order has a hidden trap in it, and must be updated or revised. Sometimes, the discovery coincides with a funeral. $\endgroup$ – KorvinStarmast Dec 9 '20 at 13:53
  • $\begingroup$ An excellent point about an aircraft's operating community "owning" the manuals and checklists for that plane, as these documents are first and foremost for the folks up in the cockpit $\endgroup$ – UnrecognizedFallingObject Dec 10 '20 at 2:17
  • $\begingroup$ @KorvinStarmast, thanks! I guess it takes one to know one... ;) $\endgroup$ – Michael Hall Dec 10 '20 at 2:21
  • $\begingroup$ With that said, if such a pilot were ever involved in an incident where the checklist being completed out of proper order was found to be directly or indirectly involved in precipitating the accident then I would imagine that said pilot would have some questions to answer. $\endgroup$ – J... Dec 10 '20 at 17:34
  • $\begingroup$ @J..., True, however, the central premise of the question is that "it doesn't matter". So, if it mattered, that would be a different scenario, right? $\endgroup$ – Michael Hall Dec 10 '20 at 21:22
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Yes, the published sequence must be respected. Here is a quote from published instructions on checklist usage by one of the major manufacturers based in the USA:

". . . . The crew may need to stop a checklist for a short time to do other tasks. If the interruption is short, continue the checklist with the next step. If a pilot is not sure where the checklist was stopped, do the checklist from the start. If the checklist is stopped for a long time, also do the checklist from the start."

If this philosophy is not already spelt out for some current aircraft types, the Regulatory bodies and Industry are (correctly) pushing it that way. Tedium is not considered as a sufficient reason to dump the C/L sequence, it is actually one reason for having a checklist!

The purpose of cockpit checklists for both Normal and Abnormal/non-Normal situations would largely be defeated if the published sequence were not followed as they are designed to ensure that the aircraft is correctly configured and safe for the next step.

In an unusual situation though (read esp: impending catastrophe), the above is to be understood in the light of the necessary disclaimer, quoted from the same manual that's quoted above:

"The flight crew must be aware that checklists cannot be created for all conceivable situations and are not intended to replace good judgment. In some situations, at the captain’s discretion, deviation from a checklist may be needed."

The statement - “ . . even if it makes no difference . . “ is a tricky one and it evokes a response of, “where do you draw the line?" - checklists are a manifestation of the need for Standardisation.

Here's a sum up, intended to complement the advice given by many on this page.

  • Checklists are made very scientifically, but even so, the endeavor is based on a best effort basis and checklist philosophy is constantly evolving.
  • instances of abnormal/non-normal situations can exist or can be conceived to support either side of the discussion.
  • Checklists are aimed at providing the highest probability of a successful outcome based on the best knowledge of the day and age.
  • Institutional Policy must be sufficiently evolved to look at variations from SOP in a practical manner.
  • A C/L sequence that regularly invites 'modification’, as reported by crew or as found by a surveillance system, requires a rethink.
  • In current day practice, ‘one off’ occurrences of a breach of checklist sequence are looked at in a benign manner by all but a few agencies.
  • As a policy, “not following the checklist sequencecannot be regularly condoned.
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I can only speak to the FAA but they expect you to follow the order that checklists are written in as per AC120-71B they also expect checklists to be created in a logical order:

4.2 Organization.

4.2.1 General Organization.

Procedures should be organized as simply as possible by order of tasking. Normal procedures are typically organized in sequence by phase of flight. When applicable, abnormal, non-normal, and emergency procedures should be organized by the triggering condition (e.g., smoke in the flight deck) rather than the potentially related system (e.g., electrical system).

...

5.3 Item Order.

The order of the items on the checklist can mirror the sequence of the flow or of the operation if the flow preceding the checklist is carefully designed to:

• Take advantage of the physical layout and location of switches, displays, and indicators in the flight deck (e.g., going from left to right, or from top to bottom);

• Account for the inherent dependencies between the systems involved;

• Support human memory; and

• Be short.

Such order aids in learning and increases ease of use. Another possible ordering consideration is item priority. The probability of interruptions and distractions increases with checklist length and the time it takes to execute it. Thus, even though checklists mainly contain critical items, these could be prioritized, and those with higher importance could be placed first on the checklist.

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On your PC, do you press the power button before it is plugged into the wall?

It is written that way because the thing might not work if you do it in the wrong order.

Your example of RADAR first and display second...If you do it the other way around, the display may have to be restarted if it sees no input from the radar.

I know in ground maintenance, you cannot get the correct reading from Step D, unless you first go through Steps A, B, and C, in that specific order.

Do it the same way, every time, line by line in the book. Muscle memory, and following the order of steps all the time, instead of some of the time. (Unless, of course, emergency conditions prohibit)

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  • $\begingroup$ If I formalized my process of plugging in a PC into a checklist it would look something like this: 1) press the power button 2) have a heart attack because it doesn't turn on 3) flip the power switch on the power supply. But I get your point. $\endgroup$ – Boris Dec 8 '20 at 17:25
  • $\begingroup$ In the example given in this answer, it definitely makes a difference. But the question specifically asked about a situation where it does NOT make a difference... $\endgroup$ – Michael Hall Dec 8 '20 at 19:06
  • $\begingroup$ "If you do it the other way around, the display may have to be restarted if it sees no input from the radar." - Is that a realistic example? I haven't worked on military aircraft, but from adjacent industries' perspectives, this sounds like very poor design. $\endgroup$ – Ruther Rendommeleigh Dec 8 '20 at 19:10
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    $\begingroup$ @Michael Hall - Checklists aren't written in isolation. Manufacturer, aircrew, maintenance all have a hand in the procedures. And they can be, and are, changed all the time. If it does not specifically make a difference, then no big problem. But should the aircrew be making that call on the fly, while in the air? If there is a question of "Why is it in this order?", then maybe address that later, on the ground. $\endgroup$ – WPNSGuy Dec 8 '20 at 21:25
  • $\begingroup$ @WPNSGuy, I agree 100%! Did you read the answer I posted? $\endgroup$ – Michael Hall Dec 8 '20 at 23:13
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It depends, in some cases there's a specific order that must be followed in order for things to work or for a safety reason.

If you look at the checklist for a PA-28 it says (among other things) to run the electric fuel pump, turn it off, prime, then start. This order pressurizes the fuel system, then aspirates fuel into the cylinders so there's something to fire when ignited. If you don't follow this exact order it won't start as there won't be fuel pressure to prime the cylinders.

Other times there's no order that has to be followed, like most pre take-off actions, but they often have an order that follows a flow across the panel, so you aren't jumping back and forth between items. It's more efficient to follow that order than make it haphazard.

So it's best to follow the order.

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