Jump to content

Archived

This topic is now archived and is closed to further replies.

sunnydaze

250 kts below 10000 ft

Recommended Posts

Hello all.

I have always set my IAS to be at 250 below 10000 ft , but I was just approaching EHAM on my last flight and at about 8000 ft I had a 30kt tail wind and an actual airspeed of 280 kts ...and I was just thinking,wouldn't it show up on the ATC radar that I was going 280 kts?

Should we be looking at actual airspeed and not just set 250 IAS ?

Thanks.

Dennis.

Share this post


Link to post

Relative to other aircraft in the air it's all equal. The pilot has to be aware of airspace though which could have lower speed limits and which crosswind component could put him into and/or tailwinds would make him enter faster. ATC's concern is seperation in the air and closing speeds between aircraft. Pilot's responsibility is knowledge of which airspace they are in.

Share this post


Link to post

ATC sees ground speed. Where I control, because the airport is already at 5,400 feet, the STARs have the planes crossing into approach airspace at about FL190 and, from the west, it's not uncommon to see them at 300+ kts even though they are restricted to 250kts

Share this post


Link to post

If you had a 30 knot tailwind and you were doing 250 knots, you'd still have an indicated airspeed of 250 knots. It is your groundspeed that would be around 280 knots.

 

ATC are aware of this kind of thing, in fact they have to be because they issue hourly ATIS reports, and at airports it dictates what runways will be in use, so if it was likely to be an issue, which it would be if you continued to have a 30 knot tailwind on approach LOL, they'd make any allowances necessary.

 

But since everyone in the same air mass would also be experiencing the same winds, the IAS would be all that was necessary to concern ATC in order to maintain spacing, because the entire air mass would be moving across the landscape at 30 knots, and everything that was flying in it would be as well, so it won't affect closure rates between aircraft very much, if at all.

 

Although it is the general rule to keep things under 250 knots below 10,000 feet, it's not always enforced, for example, some aircraft will have to fly faster than 250 knots without any flaps deployed in order to stay airborne, such as a 747 at heavy weights. So ATC do in fact often allow aircraft to pass 250 knots well below 10,000 feet. You often hear it on approach ATC actually, where ATC will say 'no speed restriction', which effectively lets the pilot decide what is the best speed to fly at. It is useful for getting things expedited when there are a lot of aircraft in a stack waiting to land too.

 

Al

Share this post


Link to post

You often hear it on approach ATC actually, where ATC will say 'no speed restriction'

 

I always thought that phrase referred to published speed restrictions on SIDs/STARs rather than the 10k foot one. In the US, regulations are specific about allowing greater than 250+ knots speed if the plane's min safe clean speed was above that, however, you are required to notify ATC. Personally, I have never actually heard that either in the real world or VATSIM.

 

But since everyone in the same air mass would also be experiencing the same winds, the IAS would be all that was necessary to concern ATC in order to maintain spacing, because the entire air mass would be moving across the landscape at 30 knots

 

Something to keep in the back everyone's mind with this is that, on VATSIM, there are several different places a plane could be getting it's weather from. FSX, REX, AS, VATSIM weather etc. Even the weather could be different depending on which VATSIM server you are signed into.

 

It's not a big deal in a terminal environment, but I've actually given up on relying on speeds to separate planes on the en route level. A controller could do everything perfectly, but there will always be discrepancies in speeds. I've even noticed that simmers using X-Plane will gain/lose separation even if they are displaying the same ground speed as an FSX plane.

Share this post


Link to post

Actually, it generally does refer to the speed restrictions on approaches when you hear ATC say 'no speed restriction' as it is generally heard in areas where they'll have a limit well below 250, but it does tell you that ATC can override the restrictions on official charts if they think it is necessary, and in any case, so can the commander of the aircraft if they feel it would compromise safety to not do that, although as you say, you'd have to advise ATC of that decision.

 

Back with the OP though, I should think it would be time to be thinking about dropping the speed below 250 anyway when you are getting down to 8,000 feet.

 

Al

Share this post


Link to post

Hello all.

I have always set my IAS to be at 250 below 10000 ft , but I was just approaching EHAM on my last flight and at about 8000 ft I had a 30kt tail wind and an actual airspeed of 280 kts ...and I was just thinking,wouldn't it show up on the ATC radar that I was going 280 kts?

Should we be looking at actual airspeed and not just set 250 IAS ?

Thanks.

Dennis.

 

The short and sweet is: Your IAS is your "actual airspeed" (for our purposes we'll avoid getting into too much terminology [just avoid using the term "actual airspeed"]). What you get over the ground is speed through the air mass +\- wind depending on the wind's direction. In other words, you used the word airspeed to describe ground speed. As far as speed restrictions go, just worry about your indicated airspeed.

 

 

Actually, it generally does refer to the speed restrictions on approaches when you hear ATC say 'no speed restriction' as it is generally in an area where they'll have a limit well below 250, but it does tell you that ATC can override the restrictions if they think it is necessary, and in any case, so can the commander of the aircraft if they feel it would compromise safety to not do that, although as you say, you'd have to advise ATC of that decision..

 

Al

 

In other words, 250kt restriction is not to be broken unless explicitly expressed or safety is a concern for PIC? (That'd be incorrect) Sorry, I'm catching up with you fella's

Share this post


Link to post

That's the trouble with FS though of course. Unless it is on VATSIM or something with a real controller, you're using canned ATC, which will pretty much stay hard and fast with the general rules, and very often the FAA ones from 2006, rather than what you'd necessarily hear right now over Europe or China or indeed many places other than the US. Which does of course have a bearing on sims when you fly out of Uncle Sam's domain.

 

That's actually why I've been persisting with Pro ATC in spite of its glitches; there's plenty of need for a decent updated ATC system for FS which takes into account modern procedures around the globe, and with a bit of luck, that might be it, particularly since we don't know when RC5 is going to show up.

 

Al

Share this post


Link to post

The UK Rules of the Air (which have legal force) read:

21 (1) Subject to paragraph (2), an aircraft shall not fly below flight level 100 at a speed

which, according to its air speed indicator, is more than 250 knots.

(2) Paragraph (1) shall not apply to:..

Share this post


Link to post

Yup, that is indeed the basic general rule you have quoted, but also read:

 

http://www.alantyson.../aics/4Y138.PDF

 

Where you will notice that the 250 knot speed limit is dependant largely on the need to see and avoid, i.e. in large part pertaining to VFR flight safety, and therefore also pertaining to flights not directly under ATC control for the purpose of either speeds, headings, altitudes or collision avoidance. Thus in certain sections of controlled airspace, and when under ATC control or for other reasons specified in that NATS circular, the 250 knot limit can indeed be overruled.

 

For an obvious example, the BAC Concorde would have not been able to even take off if that rule did not have exceptions which could be granted, and as we know, the Concorde certainly did take off. but even with less speedy jet airliners, they all pretty much climb more effectively at over 250 knots, which is another reason why the rule can also often get waived.

 

Al

Share this post


Link to post

For the avoidance of doubt, I attach Paragraph (2) in full:

 

(2) Paragraph (1) shall not apply to:

(a) flights in Class A airspace;

( B) VFR flights or IFR flights in Class B airspace;

© IFR flights in Class C airspace;

(d) VFR flights in Class C airspace or VFR flights or IFR flights in Class D airspace

when authorised by the appropriate air traffic control unit;

(e) an aircraft taking part in an exhibition of flying for which a permission is required

by article 80(1) of the Order, if the flight is made in accordance with the terms of

the permission granted to the organiser of the exhibition of flying and in

accordance with the conditions of the display authorisation granted to the pilot

under article 80(6)(a) of the Order;

(f) the flight of an aircraft flying in accordance with the A Conditions or the B

Conditions; or

(g) an aircraft flying in accordance with a written permission granted by the CAA

authorising the aircraft to exceed the speed limit in paragraph (1).

Share this post


Link to post

I have jumpseated out of Heathrow plenty of times on Heavy aircraft enroute to the far east and middle east, everytime our clean speed has been above 250kts. In fact the majority of times we were given a no speed restriction and straight up to 320 knots

 

Regards

Share this post


Link to post

You said that this was approaching EHAM. I recall reading somewhere that there is no airspeed restriction under 10,000 feet in The Netheralnds. I know i doesnt exactly answer the question, but its an interesting fact (I think).

Share this post


Link to post

Thank you all for your help and taking the time set me straight.

When I said "Actual" airspeed, I should of said TAS.

In the top left corner of the nav display there are two readouts. On my last approach they read...GS 303...TAS 262...and my IAS was 240 kts. This is what has been troubling me for a while,but with all the answers from you guys it's no longer a concern. (I'm more confused than ever!!!...only kidding) Thank you all so much.

Dennis.

Share this post


Link to post

I have jumpseated out of Heathrow plenty of times on Heavy aircraft enroute to the far east and middle east, everytime our clean speed has been above 250kts. In fact the majority of times we were given a no speed restriction and straight up to 320 knots

 

Regards

 

The reason for that is because the London CTR, the London TMA,and the Worthing CTA are all Class A airspace. See Post #11. However there is still a note on the Detling/Dover SID

 

 

6 Maximum 250KIAS below FL100 unless otherwise authorised.

Share this post


Link to post

Yup, that is indeed the basic general rule you have quoted, but also read:

 

http://www.alantyson.../aics/4Y138.PDF

 

Where you will notice that the 250 knot speed limit is dependant largely on the need to see and avoid, i.e. in large part pertaining to VFR flight safety, and therefore also pertaining to flights not directly under ATC control for the purpose of either speeds, headings, altitudes or collision avoidance. Thus in certain sections of controlled airspace, and when under ATC control or for other reasons specified in that NATS circular, the 250 knot limit can indeed be overruled.

 

For an obvious example, the BAC Concorde would have not been able to even take off if that rule did not have exceptions which could be granted, and as we know, the Concorde certainly did take off. but even with less speedy jet airliners, they all pretty much climb more effectively at over 250 knots, which is another reason why the rule can also often get waived.

 

Al

 

Are you saying that your ATC over there gives out a general 'no speed restriction' release without reference to any particular fix? Because the only time I've ever been cleared in a general way to go faster than 250 below 10,000 in the USA was during the high speed departure trials in Houston a decade ago. When ATC tells me "no speed restriction at TXMEX" it only pertains to the published crossing speed at an intersection on a SID or STAR. It doesn't mean I can break any other speed limit. For example, if a STAR had a speed restriction of 280 at a certain fix at 12,000', the no speed restriction only means that I can go fater than 250 at that fix. It still doesn't mean I can go above Mach 1. Or if there was a published speed restriction of 210 at a fix at 8,000', the 'no speed restriction at WAKEM' only means that I can cross it at up to 250. It doesn't release me to cross it at 300 knots at 8,000'.

 

Now, it I was flying a 747 at a weight whose minimum clean speed was 260, then I can go at 260 even if I was below 10,000' and ATC understands this and this is pretty normal and happens all the time. But to release planes to go faster than 250 below 10,000 for no reason is just not done in the USA. And it is not how the 'no speed restriction' phrase is used here.

Share this post


Link to post

Nah, all I was saying was that ATC can tell you 'no speed restriction', and that the 250 knots rule has exceptions. It does generally mean stuff such as 'you can go faster than the 185 knots indicated on the chart for the approach you are flying' when you here it on an approach frequency, but I was also pointing out that ATC can also allow an aircraft to blow past the 250 knot limit on a climb, and do indeed do that sometimes.

 

I hardly think that anyone is likely to interpret it as: 'Goose, it's time to buzz the tower at 500 knots' when they are on a descent to an approach or something. Although again there are exceptions, so on occasion that too can happen, since everyone has of course seen plenty or warplanes at airshows doing 400-500 knots at low level, and I have in fact been passed by RAF aircraft doing pretty near those kind of high speeds at low level on occasion when they were practicing combat flying.

 

Al

Share this post


Link to post

Are you saying that your ATC over there gives out a general 'no speed restriction' release without reference to any particular fix?

 

The answer is in the UK is yes.

 

The Detling/Dover SID I gave as an example is flown in Class A airspace to which the general rule 250kts/10000ft doesn't apply. However that rule is applied by a note on the SID. If ATC choooses it can simply say "No speed restrictions" without any reference to a fix,

Share this post


Link to post

The answer is in the UK is yes.

 

The Detling/Dover SID I gave as an example is flown in Class A airspace to which the general rule 250kts/10000ft doesn't apply. However that rule is applied by a note on the SID. If ATC choooses it can simply say "No speed restrictions" without any reference to a fix,

 

Ok. We had something similar in the US many years ago. They did it with the Houston Class B airspace, where on departure, they would say 'no speed restriction' and we could climb out at over 250. But that was ended after a few months and they have not done anything like that since anywhere else here. Problems they encountered were people hitting birds at speeds at which the planes were not designed to hit birds at, and people climbing out too shallow due to the high speeds and punching out into the undersides of the Class B airspace.

Share this post


Link to post

With regard to the OP, another thing to watch out for of course, is that some aeroplanes with retractable landing lights would have their hinge mechanism damaged at 250 knots, and it is quite common to have landing lights on below 10,000.

 

Al

Share this post


Link to post

Problems they encountered were people hitting birds at speeds at which the planes were not designed to hit birds at, and people climbing out too shallow due to the high speeds and punching out into the undersides of the Class B airspace.

 

If ATC removes ATC speed restrictions that doesn't absolve pilots from their responsibilties to fly at safe speeds and to stay within their assigned airspace. Pilots can stilll continue to fly at 250 kts - they are not obliged to fly any faster.

Share this post


Link to post
×
×
  • Create New...