Question about Airspeeds...

[VW Pilot]

OK everyone knows that below 10,000ft the speed limit is 250KTS....then 200 within lateral boundaries and c-g airports But what if you are inbound and decending through 10,000 ft to a class b airport at 250kts with a tailwind....and your ground speed is 268-270 kts.....will you be in violation? I assume controllers in class B can tell you how fast you are going on radar...so would you fly according to IAS or GS? would you decrease airspeed speed to compensate for the ground speed? (Not too slow.....) Do some Pilots do this for "just in case" or what do you do? never happened to me but it's just a question....thanks.

 

[CA1900]

OK everyone knows that below 10,000ft the speed limit is 250KTS....

Yes.

...then 200 within lateral boundaries and c-g airports

Not quite. 200 knots within 4NM of the primary airport of a Class C or D, below 2,500 feet AGL. Any other airspace that makes up the Class C or D does not have a specific speed limit.

Also note that Class B airspace does not have a speed limit. You can go through Class B at 350 knots if you want, provided you're above 10,000 MSL.

But what if you are inbound and decending through 10,000 ft to a class b airport at 250kts with a tailwind....and your ground speed is 268-270 kts.....will you be in violation?

No, you'll be fine.. The items in 91.117 all limit "indicated airspeed," not groundspeed.

would you decrease airspeed speed to compensate for the ground speed? (Not too slow.....) Do some Pilots do this for "just in case" or what do you do?

Definitely not, and at a busy airport, you'd likely give the controller a nasty surprise. If ATC wants you to go slower, he'll advise. Besides, what if you're on vectors in an airplane with nothing but a couple of VORs -- how would you even know your groundspeed?

Just take care of your airspeed; he'll take care of the rest.

 

[VW Pilot]

You asked "how would you know your grounds speed?
That was in asumption that one would be flying a jet of some sort properly equiped...or some fast flying single engine plane with Garmis GPS...Some if not all GPS recievers tell ground speed...Also pre-flight planning would tell you if you had a tailwind or not and from that you could pre-calculate your groundspeed even though it will probably differ when long before you reach your destination...(weather updates FSS or ATIS, AWOS) But as we all know weather is never as forcasted but better or worse...in most cases. Anyway thanks for the input.

 

[old*art]

You also better be doing 200 if you drop out of the bottom of the Class B ..at least in ATL.

 

[avbug]

This thread begs the question how a regulation so clear can be misunderstood or even queried...and the answer is equally clear...one must read the regulation.

§ 91.117 Aircraft speed.

(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 mph).

(b) Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.

(c) No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport or in a VFR corridor designated through such a Class B airspace area, at an indicated airspeed of more than 200 knots (230 mph).

(d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed.

How can one ask if the regulation involves groundspeed, when CLEARLY it states airspeed?

How can one ask if it really means anything but INDICATED airspeed, when it repeatedly cites indicated airspeed?

Too often we ask a question here when we should really lift a finger to help ourselves, crack open the book, and read it first.

 

[say again]

OK everyone knows that below 10,000ft the speed limit is 250KTS....then 200 within lateral boundaries and c-g airports But what if you are inbound and decending through 10,000 ft to a class b airport at 250kts with a tailwind....and your ground speed is 268-270 kts.....will you be in violation? I assume controllers in class B can tell you how fast you are going on radar...so would you fly according to IAS or GS? would you decrease airspeed speed to compensate for the ground speed? (Not too slow.....) Do some Pilots do this for "just in case" or what do you do? never happened to me but it's just a question....thanks.

Ready for a checkride?? You weren't tought well at all, seriously!! What do you do if u didnt know your GS?? Common sense goes a long way. IAS always when talking with ATC.

 

[CA1900]

You asked "how would you know your grounds speed?
That was in asumption that one would be flying a jet of some sort properly equiped...or some fast flying single engine plane with Garmis GPS...

That was my point -- there are many fast jets flying out there without any kind of advanced nav equipment. I've been in the cockpits of 737s and DC-9s that are equipped with nothing more than two VOR/DMEs and an ADF. No FMS, no GPS -- no way to determine exact groundspeed unless heading right at or away from a DME station.

Also pre-flight planning would tell you if you had a tailwind or not and from that you could pre-calculate your groundspeed...

Why are you making this more complicated than it needs to be? The regulation sets a maximum indicated airspeed. That's it.

 

[shamrock]

You weren't tought well at all, seriously!!

:blush:

 

[shamrock]

Yes.

Not quite. 200 knots within 4NM of the primary airport of a Class C or D, below 2,500 feet AGL. Any other airspace that makes up the Class C or D does not have a specific speed limit.

Also note that Class B airspace does not have a speed limit. You can go through Class B at 350 knots if you want, provided you're above 10,000 MSL.



No, you'll be fine.. The items in 91.117 all limit "indicated airspeed," not groundspeed.

Definitely not, and at a busy airport, you'd likely give the controller a nasty surprise. If ATC wants you to go slower, he'll advise. Besides, what if you're on vectors in an airplane with nothing but a couple of VORs -- how would you even know your groundspeed?

Just take care of your airspeed; he'll take care of the rest.

Damn, you's wicked smart. How you get like that?

 

[say again]

:blush:

LOL!! I guess neither was I (looks right when you're half in the bag). :beer: