A pilot reports while climbing on a SID ATC requested they be at or above an altitude they were alre...

Narrative:

We were on the departure to ZZZ; climbing to FL230 at 1500 FPM; approximately 40 NM south of ZZZ. At about 17000 ft; ATC asked us to expedite our climb to FL230. We increased our climb rate to 2000 FPM. At about FL187; ATC again told us to expedite climb and added 'I need you at FL180 in 30 seconds or less.' I responded that we were already at FL187. The controller again said 'I need you at FL180 in 30 seconds or less.' I asked the first officer if that meant the controller wanted us to go back down to FL180. He said 'I think so;' and leveled off and then began a descent to FL180. I queried the controller as to whether he wanted us back down at FL180. Simultaneously; at FL185 we got a TCAS TA showing a target at FL180 about 10 NM ahead of us; and the controller said 'expedite climb to FL230.' I took control of the aircraft; disengaged the autoplt; and began an abrupt climb. The controller then issued a heading of 270 degrees. We began the turn; re-engaged the autoplt and returned the aircraft to the first officer. The traffic alert ended immediately when we began the climb. The controller then cleared us direct ZZZ; gave us the frequency for center and then said 'thanks for your help.' for us; the main confusion began when the controller told us to be at (or above?) FL180 in 30 seconds; but we were already several hundred ft above that altitude. Then; when the controller repeated that same instruction; it added to our impression that he wanted us to go back down to FL180. Believing that he wanted us to descend; we began that action while trying to clarify what we were supposed to do. Also contributing to the confusion; the frequency was very busy. The same controller was working all the airline traffic on the departure plus several GA aircraft. While it is easy to look back and realize that we should have kept climbing to FL230; at the time I believe we did what we thought we should have done. We understood what the controller said; but the timing of it made it seem like he wanted us to do something else. Hopefully this information will help someone else avoid the same kind of confusion.

Original NASA ASRS Text

Title: A PILOT REPORTS WHILE CLBING ON A SID ATC REQUESTED THEY BE AT OR ABOVE AN ALT THEY WERE ALREADY ABOVE. THE CREW DESCENDED TO THAT ALT RESULTING IN A TCAS RA.

Narrative: WE WERE ON THE DEP TO ZZZ; CLBING TO FL230 AT 1500 FPM; APPROX 40 NM S OF ZZZ. AT ABOUT 17000 FT; ATC ASKED US TO EXPEDITE OUR CLB TO FL230. WE INCREASED OUR CLB RATE TO 2000 FPM. AT ABOUT FL187; ATC AGAIN TOLD US TO EXPEDITE CLB AND ADDED 'I NEED YOU AT FL180 IN 30 SECONDS OR LESS.' I RESPONDED THAT WE WERE ALREADY AT FL187. THE CTLR AGAIN SAID 'I NEED YOU AT FL180 IN 30 SECONDS OR LESS.' I ASKED THE FO IF THAT MEANT THE CTLR WANTED US TO GO BACK DOWN TO FL180. HE SAID 'I THINK SO;' AND LEVELED OFF AND THEN BEGAN A DSCNT TO FL180. I QUERIED THE CTLR AS TO WHETHER HE WANTED US BACK DOWN AT FL180. SIMULTANEOUSLY; AT FL185 WE GOT A TCAS TA SHOWING A TARGET AT FL180 ABOUT 10 NM AHEAD OF US; AND THE CTLR SAID 'EXPEDITE CLB TO FL230.' I TOOK CTL OF THE ACFT; DISENGAGED THE AUTOPLT; AND BEGAN AN ABRUPT CLB. THE CTLR THEN ISSUED A HDG OF 270 DEGS. WE BEGAN THE TURN; RE-ENGAGED THE AUTOPLT AND RETURNED THE ACFT TO THE FO. THE TFC ALERT ENDED IMMEDIATELY WHEN WE BEGAN THE CLB. THE CTLR THEN CLRED US DIRECT ZZZ; GAVE US THE FREQ FOR CTR AND THEN SAID 'THANKS FOR YOUR HELP.' FOR US; THE MAIN CONFUSION BEGAN WHEN THE CTLR TOLD US TO BE AT (OR ABOVE?) FL180 IN 30 SECONDS; BUT WE WERE ALREADY SEVERAL HUNDRED FT ABOVE THAT ALT. THEN; WHEN THE CTLR REPEATED THAT SAME INSTRUCTION; IT ADDED TO OUR IMPRESSION THAT HE WANTED US TO GO BACK DOWN TO FL180. BELIEVING THAT HE WANTED US TO DSND; WE BEGAN THAT ACTION WHILE TRYING TO CLARIFY WHAT WE WERE SUPPOSED TO DO. ALSO CONTRIBUTING TO THE CONFUSION; THE FREQ WAS VERY BUSY. THE SAME CTLR WAS WORKING ALL THE AIRLINE TFC ON THE DEP PLUS SEVERAL GA ACFT. WHILE IT IS EASY TO LOOK BACK AND REALIZE THAT WE SHOULD HAVE KEPT CLBING TO FL230; AT THE TIME I BELIEVE WE DID WHAT WE THOUGHT WE SHOULD HAVE DONE. WE UNDERSTOOD WHAT THE CTLR SAID; BUT THE TIMING OF IT MADE IT SEEM LIKE HE WANTED US TO DO SOMETHING ELSE. HOPEFULLY THIS INFO WILL HELP SOMEONE ELSE AVOID THE SAME KIND OF CONFUSION.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	793147
Time
Date	200806
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : zzz.vor
State Reference	US
Altitude	msl single value : 18000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial
Route In Use	departure sid : abc
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 88 flight time total : 6750 flight time type : 5564
ASRS Report	793147
Events
Anomaly	altitude deviation : undershoot non adherence : clearance
Independent Detector	aircraft equipment : tcas other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

A pilot reports while climbing on a SID ATC requested they be at or above an altitude they were already above. The crew descended to that altitude resulting in a TCAS RA.