Airspeed Restrictions

[BoilerPilot]

OK Guys and Gals...

This came up between in a table conversation the other day and wanted to get input from others...

The scenario is...
Citation N12345 is enroute to STL. In the descent KC Center tells N12345 to maintain 290 knots. Then...N12345 is told to cross 40 SW of St. Louis at 11,000 and 250.

The question...

Where does the airspeed reduction take effect? Is it like altitude so long as you make the restriction it doesn't matter? Does it have to be between 290 and 250?

Just thought it was interesting.

 

[Hold West]

OK Guys and Gals...

This came up between in a table conversation the other day and wanted to get input from others...

The scenario is...
Citation N12345 is enroute to STL. In the descent KC Center tells N12345 to maintain 290 knots. Then...N12345 is told to cross 40 SW of St. Louis at 11,000 and 250.

The question...

Where does the airspeed reduction take effect? Is it like altitude so long as you make the restriction it doesn't matter? Does it have to be between 290 and 250?

Just thought it was interesting.

Air traffic control instructions are not magic - they are very literal. "Cross 40 SW of STL at 11,000 and 250 knots" means exactly that: be at 11,000 and 250K 40 SW of STL. What you do before 40 SW of STL is up to you.

If I want you to slow down, then descend, I'll say so: "Reduce speed to 250 knots, and cross 40 miles SW of STL at 11,000".

If I want you to descend now, then make the speed later: "Descend and maintain 11,000, cross 40 SW of STL at 250K".

If I want you to defy the laws of physics, I'll say that too: "Descend now maintain 11,000, expedite your descent, reduce speed to 250K in the next 20 miles".

 

[GravityHater]

If I want you to defy the laws of physics, I'll say that too: "Descend now maintain 11,000, expedite your descent, reduce speed to 250K in the next 20 miles".

I had that twice this weekend. One like you posted and:

"I need best forward speed and your best rate through 230."
"OK, I'll light the rockets fer ya."

 

[Hook 'Em Horns]

Sounds to me like the controller wants the Citation to descend at 290 KIAS, then level at 11,000 and slow to 250 KIAS 40 sw of St. Louis.

Unless the controller said "Resume normal speed " prior to issuing the crossing resriction, then the crew is required to maintain the previously issued speed of 290 KIAS. Reference: AIM 4-4-11 Speed Adjustments

4-4-11,f. If ATC determines (before an approach clearance is issued) that it is no longer necessary to apply speed adjustment procedures, they will inform the pilot to resume normal speed.

 

[BoilerPilot]

Thanks for the replies...I had looked for that AIM reference but never found it for some reason. That does sound like it's a 290 until the 250 crossing. Appreciate the insight.

 

[rubicon789]

:laugh: Citations don't do 290... unless it's a 7... But for real, I say desend with the speed, don't slow down. Get the 250 at the crossing restriction and no sooner. Save the time, go fast.

 

[Hold West]

Sounds to me like the controller wants the Citation to descend at 290 KIAS, then level at 11,000 and slow to 250 KIAS 40 sw of St. Louis.

Unless the controller said "Resume normal speed " prior to issuing the crossing resriction, then the crew is required to maintain the previously issued speed of 290 KIAS. Reference: AIM 4-4-11 Speed Adjustments

4-4-11,f. If ATC determines (before an approach clearance is issued) that it is no longer necessary to apply speed adjustment procedures, they will inform the pilot to resume normal speed.

Each subsequent clearance automatically cancels the previous one. "Maintain 290 kts" is one. "X 40SW STL @ 250K" is another. Unless given together somehow, say "Maintain 290 kts until reaching 11,000, then reduce speed to 250", one cancels the other.

 

[Flyerjosh]

Each subsequent clearance automatically cancels the previous one. "Maintain 290 kts" is one. "X 40SW STL @ 250K" is another. Unless given together somehow, say "Maintain 290 kts until reaching 11,000, then reduce speed to 250", one cancels the other.

True, but most controllers out here on the east coast expect you to maintain the 290 until reasonably close to the crossing restriction. Otherwise expect to get yelled at.

 

["Next Wave"]

Heard this before?

"These airbrakes are for my mistakes not yours" (Mr. controller)

UNABLE!!!!!

 

[AWACoff]

I have a similiar question. We had a restriction of cross XYZ at 10000 and 250. My FO and I got too busy talkin' and not enough flying. I caught the missed descent late and he headed down like a baron full of doctors. We changed frequencies and the new controller gave us "descend to 6000 and turn right to 180". My understanding is that the crossing restriction has been cancelled due to a new clearance without a restatement of the the old restriction. My FO disagreed. The AIM seems to agree with me. Who's right?