Questionnaires and Appraisal
Betty Girl,
Please don’t take this personally (!), as I and the many who observe this and ‘the other’ thread are very grateful for your continual contributions. 
But I do have to observe that a reluctance to appraise some staff as being lower performers than others is one of the hurdles that a good manager must overcome. You mentioned that: “it is also not good practice to encourage people to assess their staff, making the assumption that a certain percentage must be below standard either.” Well, it’s not just semantics, but someone may be performing perfectly adequately, and delivering ‘to standard’, but they may be only a satisfactory performer compared to others who are very good or excellent.
The inevitability is that the performance of individuals in a group will fall into some sort of normal distribution, the classic bell curve. Often it may be very hard to identify differences between the high and low performers; that means that the bell curve is very narrow. But within that population, the average performance is, by definition, 1.0; and if one has someone who is ‘excellent’, and one wants to rank them as a 1.2, then one has to rank someone as a 0.8, or perhaps two folk as 0.9. Ranking everyone as at least 1.0, and then some as 1.1, and a few as 1.2 means an increase in the average… and so the folk ranked as 1.0 are coming out as below average; that’s what it means.
Tough, isn’t it? And made all the more tough by your modus operandi, where you are working as a virtual team, and not able to observe people for more than the duration of perhaps two flights.