S

Steve

Well Known Member
After receiving my departure instructions from Salt Lake Clearance Delivery last evening, the controller responded with "Say type aircraft and speed."
The first part is easy but what "speed" is he after? IAS? CAS? Ground speed? Knots or statute? I realize he's plannnig for an orderly departure flow so what data would be best for his purposes?

Steve
 
I'm no expert, but I believe all speeds assigned by and reported to ATC are to be IAS. Every aircraft is required to have an airspeed indicator, but not a CAS/TAS calculator or GPS to calculate ground speed.
 
IAS

Jamie and Mike are correct. They ALWAYS want IAS in knots!

CONQUEST I Driver
 
IAS

Because its all relative. You can always get two guys or more to fly the same IAS to establish and maintain separation. IFR guys will be flying a filed IAS and asking you your aircraft type and speed allows ATC to slot you into the system. We're always asked for IAS or Mach (same thing just referenced to speed of sound). Works like a charm to provide separation.
 
ias it is

We want ias but our readout on the scope is that of ground speed. BTW...it does not always workout so well...due to altitude changes during sequencing. 1st acft @12000 and 2nd acft descending from fl240 to 12000. I teach our trainees that they can expect 7kts per 1000/ft if both acft are assigned the same ias. That is why we slow you down then speed you back up a bit once we have established spacing. Well that's from a center point of view.

Take care and good topic.....
 
Between winds, angle intercepts, and altitudes and other complexities, it would seem that someone managing positioning and sequence all the time would always want one number that meant the same to all in all senerios, that being groundspeed. Is there anyone flying in the system today that doesnt have ground speed? I suppose there are, but in very small numbers.
Seems one less task on the controllers to deal with if they all could just use ground speed.
 
The problem with that is that then you redesign all the approach and departure paths, and suddenly any change in wind will FUBAR your angles and speeds. The pilot is less aware on a minute-by-minute level of what the winds are than the controller. IAS lets the pilot concentrate on what he (or she) is doing without task saturation in the cockpit trying to maintain a given groundspeed while flying through various wind levels.

If the controller assigns 210 knots to incoming turbines, and consistently sees 235 groundspeeds, it's not gonna take long for him to realize he's +25 with wind at that level and adjust assigned speeds accordingly if needed. If you tried to get EVERY pilot in that string of airplanes to make the adjustment based on a groundspeed that is affected by a continually changing windspeed in climb/descent, you would end up with some sharp guys making the adjustment fast and some dumb ones screwing it up, resulting in an unholy mess very quickly. It's easier for one man (controller) to adjust rather than expecting many (the pilots) to get it right.

I've seen enough stupid human tricks in the air to believe that in many, if not most, cases the controller has a better chance of keeping it straight than the pilots. If we were all professional, nimble-minded, and very current it would work fine - but that's not reality.
 
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when the tower asks for my heading, or asks me to steer heading, I've always assumed they meant magnetic, but always wondered about this. I guess they know all the winds and your speed, and do the ground track calcluations themselves (or on computer).
 
Steve said:
The first part is easy but what "speed" is he after? IAS? CAS? Ground speed? Knots or statute? I realize he's plannnig for an orderly departure flow so what data would be best for his purposes?
Click to expand...

This would be a good refrence before you go flying next time.
Hope this helped
http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/aim/index.htm

Controller.

1. Assigns speed adjustments to aircraft when necessary but not as a substitute for good vectoring technique.

2. Adheres to the restrictions published in the FAAO JO 7110.65, Air Traffic Control, as to when speed adjustment procedures may be applied.

3. Avoids speed adjustments requiring alternate decreases and increases.

4. Assigns speed adjustments to a specified IAS (KNOTS)/Mach number or to increase or decrease speed using increments of 10 knots or multiples thereof.

5. Advises pilots to resume normal speed when speed adjustments are no longer required.

6. Gives due consideration to aircraft capabilities to reduce speed while descending.

7. Does not assign speed adjustments to aircraft at or above FL 390 without pilot consent.

http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/aim/Chap5/aim0505.html#5-5-9
 
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speed

Just a point of clarification: I was on the ground getting my departure briefing (Class Bravo airspace) when I was asked aircraft type and speed. I'm flying a -9A. I can comfortably fly anywhere from 60 to 140 mph indicated (no gear fairings installed yet).
The controller was content with my "type RV, 140 indicated" answer.

Steve
 
prkaye said:
when the tower asks for my heading, or asks me to steer heading, I've always assumed they meant magnetic, but always wondered about this. I guess they know all the winds and your speed, and do the ground track calcluations themselves (or on computer).
Click to expand...

If your in the air, use your mag compass (with var correction)

On the ground use true north i.e. winds on atis
 
Steve said:
Just a point of clarification: I was on the ground getting my departure briefing (Class Bravo airspace) when I was asked aircraft type and speed. I'm flying a -9A. I can comfortably fly anywhere from 60 to 140 mph indicated (no gear fairings installed yet).
The controller was content with my "type RV, 140 indicated" answer.

Steve
Click to expand...
Alway specifie speed, in (indicated knots) unless asked diffrent by ATC

This will greatly help the traffic around you as well, i.e. traffic inbound to teminal area.

4-2-11. Speeds ​
The separate digits of the speed followed by the word "KNOTS." Except, controllers may omit the word "KNOTS" when using speed adjustment procedures; e.g., "REDUCE/INCREASE SPEED TO TWO FIVE ZERO."
http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/aim/Chap4/aim0402.html#4-2-11
 
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sonny junell said:
...On the ground use true north i.e. winds on atis
Click to expand...
ATIS winds are magnetic. www.flightsafety.org/alar/alar_bn8-6-wind.pdf

Also, when ATC asks you your speed you are supposed to tell them what it says on the airspeed indicator, agreed, but in the case of asking what your speed is by clearance delivery, I don't think that has been answered, and it has never happened to me. I don't see how you can give a predicted IAS as that will very great over the flight, especially if you go to a high altitude. It seems to me more logical that they would want your TAS cruising speed, such as you would enter in a flight plan.

As for you folks that report your IASs are 160 and 165 knots I can only go WOW, you must fly at lot at very high power settings at very low altitudes. I would guess an average IAS for me, in cruise is about 135 knots and I usually fly pretty fast, but at a pretty high altitude.
 
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cd wanting to know airspeed

the only reason I can think of why clearance would want to know speed is because he is typing a vfr flightplan in the national airspace system via flight data input output. once this happens you depart the controller "DM"'s you..departure message and flight progress strips go to the affected sectors and facilities. In the center we have shortcut keys for all this speeding things up quite a bit.

Hope this helps...

As far as controlling via ground speeds...well that would be tough too when you are sequencing from different angles where the jetstream is a huge factor. we start sequencing for miami and fort lauderdale 150 miles out during busy periods...
 
Use IAS

Not all airplanes are equiped with GPS and can determine ground speed at a moments notice. Unless someone is a student pilot, I suspect that there are not many folks pulling out their trusty flight calculators and doing the math between checkpoints. They do contain an ASI. Also - I've never been told to maintain a ground speed.

Say type - that little blimp on the radar doesn't tell them how fast you can fly. C172 - you might be able to give him a 120 knots on a good day. Experimental RV - 120 knots not even an issue (well, maybe on a 12).

Speaking of say type and speed - funny story. I was at a FAA safety meeting and a blimp pilot told a great story. He asked for direct to final and was denied. He then requested the full procedure for the ILS (can you say 45 minutes) since he could not get direct. The controller then asked if he still wanted direct and then granted permission.

More than 1 way to skin a cat!!!
 
Purpose: Flight Plan or Airborn Control

n5lp said:
but in the case of asking what your speed is by clearance delivery, I don't think that has been answered.
Click to expand...

I was thinking along the same lines as Larry. Since it was Clearance asking, it sounded like they may have needed a planned TAS as used in a flight plan. I've filed a couple times over the radio (flight plan was dropped, and a willing CD controller took the data and filed for us, rather than making us call FSS or company dispatch to file for us) and in those cases they needed filed TAS.

Never had CD ask for type and speed out of the blue though...so it is a bit confusing. I probably would have given him TAS, after my brain stopped smokin' from figuring it out! ;) Or I'd have asked him which he wanted...most of the ATC bubbas won't yell at ya too much for askin'! :)

As the others have said, if you're airborne, it's definitely IAS. Probably better for us on the throttle end of the radio, 'cause it's straithforward...if they wanted groundspeed, we'd have to change IAS every time we turned to hold a constant GS (unless wind is calm)...too much work! :eek:

Anyway, just thoughts...the CD piece and you being on the ground at the time of the request puts a subtle twist in this that Larry caught. Good discussion!!

Cheers,
Bob
 
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How fast is it?

ATC wants to know are you 250kts (jets) or 100kts (GA) or something in-between.

I am surprised at 165kts in a climb, level I can see that. I believe it, no doubt. And my girlfriend is a Victoria secrets model and my dog won the Westminster dog show. :rolleyes: (kidding)
 
I'm always thrown off when I get in a plane that has an ASI that shows MPH (or that has MPH on the outer dial and Knots on the inner)... :)
 
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