Circuitous routes out of Biggin Hill

[SpringHeeledJack]

I have idly noticed every now and then that certain aircraft (usually powerful single and twin props) heading generally West from Biggin Hill do a long-ish departure to the East and South steadily climbing up above traffic in and around London. I can understand why this might be necessary for the more feeble prop planes ;-) but for the more powerful and capable props it seems a waste of fuel and time. Obviously it is deemed necessary by ATC, so would someone be kind enough to explain why please ?

[eckhard]

All published Standard Instrument Departures from Biggin Hill route towards Detling VOR initially. DET is 21 nms east of Biggin Hill. From there, published routes continue mostly to the north-east, east and south-east; the only exception is the route towards Brookman’s Park, Henton and then Compton.

ATC May of course offer earlier westerly routings, once under radar control, without the need to fly over DET.

The initial route keeps traffic clear of London City, Gatwick and Heathrow and this is probably the reason for the 21nm easterly route before any turns are published.

[treadigraph]

I very occasionally see traffic inbound to Biggin and London City pass eastwards over Biggin at perhaps 15000' and descend over Kent before heading westbound to join the appropriate approach. Usually BA's A318 or Cityjet RJ85s for LCY and bizjets for Biggin.

[chevvron]

I have idly noticed every now and then that certain aircraft (usually powerful single and twin props) heading generally West from Biggin Hill do a long-ish departure to the East and South steadily climbing up above traffic in and around London. I can understand why this might be necessary for the more feeble prop planes ;-) but for the more powerful and capable props it seems a waste of fuel and time. Obviously it is deemed necessary by ATC, so would someone be kind enough to explain why please ?
A Biggin departure routing west via OCK would need to be climbed through the OCK hold, which is delegated to Heathrow Approach, thus it would need extra co-ordination to climb into CAS hence the extended routing for IFR departures.

[SpringHeeledJack]

Thankyou all for the detailed explanations as to why these routings should be.

[Council Van]

This video doesn't include Biggin Traffic but does show all the arrivals and departures for the 5 big airports and demonstrates the lack of airspace available for aircraft to climb through to the West of Biggin.
(If the link doesn't work then search 'nats 24 layers of london' in youtube.)
https://www.google.com/url?sa=t&source=web&rct=j&url=%23&ved=2ahUKEwjQqvSprJzlAhVKecAKHbigA6UQwqsBMAB6BAgGEAQ&usg=AOvVaw0VTJzWxrN8ZFOD4xbU2nov

[chevvron]

Thankyou all for the detailed explanations as to why these routings should be.
It's a similar problem for airports to the south west of Heathrow; departures from the Blackbushe/Fairoaks/Farnborough area wishing to exit UK airspace at Dover have to route southwards via Goodwood then eastwards via Seaford and along the south coast.

[jimjim1]

Could be worse -

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/881x768/delhi_tashkent_0febf9c43b01df1e655eb60f1f45fe334611822f.png

[Council Van]

Could be worse -

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/881x768/delhi_tashkent_0febf9c43b01df1e655eb60f1f45fe334611822f.png
https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/720x1440/screenshot_20191018_213919_c4eae9c7dfbad6542ffd1979bbedb63c1 6fcca12.png
Tel Aviv is similar for East bound departures due to the political situation.