fox5,
While you're doing the Maths, could you help out by factoring in a very basic
and fundamental principle that NPAS
seem to have omitted :
NPAS have published maps depicting their now infamous "20 minute" range circles,
that indicate the proposed coverage under their 20 Base plan.
These maps appear to have been used to persuade Chief Constables and Police Authorities around the UK,
that they will receive a service that is more effective and will costs less.
The point has been raised previously elsewhere, and to my knowledge has not been contradicted,
( so I can only assume it is correct ), which is that the 20 minute circles
have been
calculated incorrectly on the assumption that the aircraft
is travelling at a constant speed throughout the journey - from skids off to arrival,
( did they use 120 Kts or 120 MPH ? - The Circles seem to represent about 30 miles radius ),
when in reality of course, unless deploying while already at Transit speed and directly overhead the Base,
the aircraft starts from Base at 0 Kts, will have varying departure profiles depending on wind speed and direction,
and other factors that may preclude departing directly on track, BEFORE accelerating up to Transit Speed,
and then slowing down again as the target location is reached.
This basic principle means that the published 20 minute circles,
on which decisions as to whether to sign up to NPAS or not are being made,
may be WRONG and that the actual area that can be covered in 20 minutes is LESS.
( Of course it is accepted that there are times when aircraft WILL already be airborne
and on such occasions deployment times
may be shorter, but generally most deployments are made from Base ).
The attached NPAS coverage map ( from the Public Domain ) illustrates the point nicely,
as there are also some "15 minute" circles - which in my very humble and unsupported opinion,
are probably more realistic of the area that COULD be covered in 20 minutes,
especially when taking into account that those 15 minute circles
have probably also been calculated with the same flawed mathematical assumption of constant aircraft speed.
So, all that needs to be factored in AFTER the above, is an examination of the time taken under existing practices -
from from when a person ( such as a PC ) at the scene of an incident requests Air Support,
to the time that the request reaches the ASU staff and a decision is made to deploy,
compared with the time taken to achieve this under any NPAS deployment plan, such as via a Regional or National Control Room,
with any additional time taken reducing the "20 minute" circles, and thus reducing effective coverage, even further.
A few Purple patches in there amongst the 15 minute circles
