250kt's Below 10,000??

[carbonfibre]

While doing my ATPL's i always believed it was 250 below 10,000 unless "no speed" was instructed by ATC, but was used more commonly for departure?

I have now read in a book that it can be 250 or Vref + 100kt's whichever is the slower? i.e. a 747 with a Vref of 165 could be doing 265 below 10,000, I can understand this with heavy aircraft and would like clarification.

Thanks for any replies in advance


:ok:

[Spitoon]

The law's the law (well this is what is is in the UK anyway) Rule 23
(1) Subject to paragraph (3), an aircraft shall not fly below flight level 100 at a speed which according to its air speed indicator is more than 250 knots unless it is flying in accordance with the terms of a written permission of the Authority.
(2) The Authority may grant a permission for the purpose of this rule subject to such conditions as it thinks fit and either generally or in respect of any aircraft or class of aircraft.
(3) Paragraph (1) shall not apply to:
(a) flight in Class A airspace;
(b) VFR flight or IFR flight in Class B airspace;
(c) IFR flight in Class C airspace;
(d) VFR flight in Class C airspace or VFR flight or IFR flight in Class D airspace when authorised by the appropriate air traffic control unit;
(e) the flight of an aircraft taking part in an exhibition of flying for which a permission under article 61 of the Order is required, if the flight is made in accordance with the terms of a permission granted to the organiser of the exhibition of flying under article 61 of the Order, and in accordance with the conditions of a display authorisation granted to the pilot under article 61 of the Order; or
(f) the flight of an aircraft flying in accordance with the ‘A Conditions’ or the ‘B Conditions’ set forth in Schedule 2 to the Order.
I can't fathom out para (f) but unless that gives you an out for Vref +100 it's a blanket ban on 250kts+ in airspace where you might meet VFR traffic that's not talking to anyone.

[Shamrock 602]

Hi carbonfibre,

Am I being dense, or might you have got this the wrong way around?

> I have now read in a book that it can be 250 or Vref + 100kt's
> whichever is the slower? i.e. a 747 with a Vref of 165 could be
> doing 265 below 10,000, I can understand this with heavy
> aircraft and would like clarification.

The slower of 250 kts and 265 would still be 250. If the rule does exist (maybe in the Schedule referred to in Spitoon's posting), and if it is a case "whichever is the slower", it would mean that aircraft with Vref of less than 150 would be restricted to less than 250 below FL 100.

By the way, what would 250 IAS be in TAS around that altitude?


Cheers,

Shamrock 602

[Easy226]

With an IAS of 250 Kts at FL100 and assuming ISA conditions ( -5 degress at FL100), the TAS will be around 290 kts.
Many Thanks
Dan

[carbonfibre]

Shamrock yes you are right , i wrote this the wrong way around , it is whichever is the greater!!

It does not mention TAS so i assumed as it is referenced to IAS, this is what this meant, so here is the exact wording for you all

The maximum speed below 10,000 is 250kt's, or Vref + 100, whichever is the greater.

In this book it has reached 265 by 4300ft.

Spitoon, i can only assume that this was a Heathrow departure that the flight in class A airspace applies

Thanks for the replies:ok:

[Shamrock 602]

Hi carbonfibre and all,

No probs, I have days like those too! Thanks for the info on TAS/IAS.

Shamrock 602

[scroggs]

The spped flown will be either 250 kts or the minimum safe speed as determined by the pilot, whichever is the greater. The minimum safe speed is usually the minimum clean speed for the weight. On a B747 or A340-600 (and others) that will frequently be significantly above 250kts at heavy weights.

No AT controller will argue if a pilot says that, say, 280 is his minimum, but that pilot may have to accept vectors to ensure separation from similarly-routed traffic.

[Spitoon]

scroggs rightly says that a controller is unlikely to tell a pilot that he/she can't fly at their minimum safe speed.

But the law still stands and unless sub-para f) gives an out - and I still cant work out or find what it actually means - we could end up with the daft situation where a controller is asked to condone a breach of the law! Can a heavy B747 or EA34 get off any of the UK's regional airports? Particularly those that aren't connected to the airway system and where it's inevitable that the aircraft will fly outside CAS.