Originally Posted by
bad bear
TCAS FAN, "I refer you to UK AIP ENR 1.6, para 1.4.1 which specifies this." very interesting ! I would love to know why the procedure allows a platform at 1,500' where the base is 2,000'. I feel sure there is a story there? it looks at first glance that an aeroplane maintaining 2,500 to the west and be within the airspace till capturing the glide but I guess not.
Its a very long and complex story. The RWY 08 ILS instrument approach procedure is designed in accordance with ICAO PANS OPS Doc 8168, as adopted by the UK. This specifies descent gradients which are applied with regards to the surrounding obstacle environment. BOH is fortunate in that surrounding obstacles permit a descent to 1500 FT on the outbound leg of the IAP, thereby keeping the overall track miles necessary to fly the procedure to a minimum.
The instrument approach descent profile should be considered when designing Controlled Airspace, in that an ICAO Annex 11 Standard, which the UK said it complied with but ignored when the present Controlled Airspace was designed in the late 1980s, required (and still does) that IAP are enclosed within Controlled Airspace.
I am not aware of any action taken by the BOH airport operator, past or present, to resolve this issue.
Radar vectoring to the IAP will require sufficient track miles to permit ATC to provide a base leg and then a closing heading to intercept the LLZ, with ideally a period of level flight before GP intercept. Hence the IAP entry to warn of the likelihood of leaving Controlled Airspace, which should of course be of adequate extent (IAW Annex 11) to contain aircraft within.