B737-400 flight crew found it impossible to make a crossing restr which they had accepted from ATC. ...

Attributes
ACN	328110
Time
Date	199602
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : air
State Reference	OH
Altitude	msl bound lower : 21000 msl bound upper : 22500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute airway : zid
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : instrument
Experience	flight time last 90 days : 68 flight time total : 13892 flight time type : 2932
ASRS Report	328110
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : undershoot altitude deviation : crossing restriction not met non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : insufficient time other
Consequence	Other
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

We were cleared direct air in a descent to FL240 with no restrs or expected restrs other than the typical cross wiske at 10000 ft. That had been programmed in the FMC but had not been given to us yet. We were well below the profile for the crossing. Approximately 47-50 NM southwest of air when the controller issued 'cross 35 NM southwest of air at FL210.' my first officer read back the clearance as I was resetting the altitude alerter. As I was starting to consider exactly where we were, the controller added 'do the best you can.' this alerted us to the possibility that it might not be possible. I immediately verified that we had idle power then deployed the speed brake. It took a couple of mi, but I realized that we were going to miss the restr by a small amount. I advised the controller 'unable to make the restr but will do the best we can with maximum effort.' I was expecting him to either lift the restr or give us a vector but he didn't respond. We were already assigned maximum forward airspeed for spacing so a vector would be counter-productive. There was no observed (TCASII) traffic and as soon as we leveled at FL210 he switched us to ZOB, so my guess is that the restr was due to a LOA between ctrs not for expected traffic conflicts. With the FMC we have lots of help making known or expected restrs, but with the lack of advance knowledge we had no way to know if we were on a profile to make it. Without programming that takes some time. Had I been the first on the radio to respond I would have accepted the altitude clearance and that we would advise shortly whether we could make and accept the restr. As it was, the controller apparently realized moments after he gave us the restr that it was unlikely that we could make it. He should have issued an amendment immediately instead of just leaving us hanging, especially, after I advised 'unable' approximately 8 mi before the crossing.

Original NASA ASRS Text

Title: B737-400 FLC FOUND IT IMPOSSIBLE TO MAKE A XING RESTR WHICH THEY HAD ACCEPTED FROM ATC. ATC DID NOT COMMENT WHEN THE CREW LATER STATED THAT THEY COULD NOT COMPLY WITH THE CLRNC.

Narrative: WE WERE CLRED DIRECT AIR IN A DSCNT TO FL240 WITH NO RESTRS OR EXPECTED RESTRS OTHER THAN THE TYPICAL CROSS WISKE AT 10000 FT. THAT HAD BEEN PROGRAMMED IN THE FMC BUT HAD NOT BEEN GIVEN TO US YET. WE WERE WELL BELOW THE PROFILE FOR THE XING. APPROX 47-50 NM SW OF AIR WHEN THE CTLR ISSUED 'CROSS 35 NM SW OF AIR AT FL210.' MY FO READ BACK THE CLRNC AS I WAS RESETTING THE ALT ALERTER. AS I WAS STARTING TO CONSIDER EXACTLY WHERE WE WERE, THE CTLR ADDED 'DO THE BEST YOU CAN.' THIS ALERTED US TO THE POSSIBILITY THAT IT MIGHT NOT BE POSSIBLE. I IMMEDIATELY VERIFIED THAT WE HAD IDLE PWR THEN DEPLOYED THE SPD BRAKE. IT TOOK A COUPLE OF MI, BUT I REALIZED THAT WE WERE GOING TO MISS THE RESTR BY A SMALL AMOUNT. I ADVISED THE CTLR 'UNABLE TO MAKE THE RESTR BUT WILL DO THE BEST WE CAN WITH MAX EFFORT.' I WAS EXPECTING HIM TO EITHER LIFT THE RESTR OR GIVE US A VECTOR BUT HE DIDN'T RESPOND. WE WERE ALREADY ASSIGNED MAX FORWARD AIRSPD FOR SPACING SO A VECTOR WOULD BE COUNTER-PRODUCTIVE. THERE WAS NO OBSERVED (TCASII) TFC AND AS SOON AS WE LEVELED AT FL210 HE SWITCHED US TO ZOB, SO MY GUESS IS THAT THE RESTR WAS DUE TO A LOA BTWN CTRS NOT FOR EXPECTED TFC CONFLICTS. WITH THE FMC WE HAVE LOTS OF HELP MAKING KNOWN OR EXPECTED RESTRS, BUT WITH THE LACK OF ADVANCE KNOWLEDGE WE HAD NO WAY TO KNOW IF WE WERE ON A PROFILE TO MAKE IT. WITHOUT PROGRAMMING THAT TAKES SOME TIME. HAD I BEEN THE FIRST ON THE RADIO TO RESPOND I WOULD HAVE ACCEPTED THE ALT CLRNC AND THAT WE WOULD ADVISE SHORTLY WHETHER WE COULD MAKE AND ACCEPT THE RESTR. AS IT WAS, THE CTLR APPARENTLY REALIZED MOMENTS AFTER HE GAVE US THE RESTR THAT IT WAS UNLIKELY THAT WE COULD MAKE IT. HE SHOULD HAVE ISSUED AN AMENDMENT IMMEDIATELY INSTEAD OF JUST LEAVING US HANGING, ESPECIALLY, AFTER I ADVISED 'UNABLE' APPROX 8 MI BEFORE THE XING.

Data retrieved from NASA's ASRS site as of July 2007 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.

B737-400 flight crew found it impossible to make a crossing restr which they had accepted from ATC. ATC did not comment when the crew later stated that they could not comply with the clearance.