Narrative:

A B767-300 aircraft. On engine startup in ZZZZ; got a duct leak light. Went back to gate. Turned out to be a minor leak in the center pneumatic duct in the wheel well near the air driven pump (adp). The mechanics said you could tell the seals were very old and you could see it had been leaking for a while; but not enough to trip the sensor or do any damage. The summer heat in ZZZZ added enough heat along with the leak to trip off the sensor. Replacement seals were put on the next flight down to ZZZZ. The [flight] crew and even some passengers were stuck in ZZZZ for 48 hours. No doubt; this problem cost the company a lot of money. For those reading this who are not familiar with the 767-300; the center pneumatic duct is the heart of the hydraulic and pneumatic system. The center duct supplements the center hydraulic system for high load items with an adp. The adp is also required to power the hydraulic motor generator (hmg) when the main buses are inoperative. So the center pneumatic duct is a very important item; especially in areas where diversion airports are scarce; like in south america and over the atlantic. I don't know the design of these seals; but this brings out a few safety thoughts that brings me to writing this: 1) the B767-300 aircraft operates to south america and europe (ETOPS). 2) once these seals have started a minor leak; how long until they become a major leak? 3) the mechanics said you could tell that these pneumatic duct seals were really old. 4) what are the consequences if a failure of an old seal occurs at a critical time; e.g. Already in an emergency situation and your down to hmg operation over the atlantic or south america where airports are few? 5) another incident like this can cost the company a lot more money. Seems to me in the interest of safety and long term company cost of a failure at the wrong time; that all old duct seals should be replaced on all 767-300 aircraft.

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Original NASA ASRS Text

Title: A B767-300 flight crew returned to the gate after engine startup due to an illuminated Duct Leak light. Old; dried seals for the center pneumatic system duct in the wheel well near the air driven pump (ADP) caused the leak.

Narrative: A B767-300 aircraft. On engine startup in ZZZZ; got a Duct Leak light. Went back to gate. Turned out to be a minor leak in the center pneumatic duct in the wheel well near the air driven pump (ADP). The Mechanics said you could tell the seals were very old and you could see it had been leaking for a while; but not enough to trip the sensor or do any damage. The summer heat in ZZZZ added enough heat along with the leak to trip off the sensor. Replacement seals were put on the next flight down to ZZZZ. The [flight] crew and even some passengers were stuck in ZZZZ for 48 hours. No doubt; this problem cost the company a lot of money. For those reading this who are not familiar with the 767-300; the center pneumatic duct is the heart of the hydraulic and pneumatic system. The center duct supplements the center hydraulic system for high load items with an ADP. The ADP is also required to power the hydraulic motor generator (HMG) when the main buses are inoperative. So the center pneumatic duct is a very important item; especially in areas where diversion airports are scarce; like in South America and over the Atlantic. I don't know the design of these seals; but this brings out a few safety thoughts that brings me to writing this: 1) The B767-300 aircraft operates to South America and Europe (ETOPS). 2) Once these seals have started a minor leak; how long until they become a major leak? 3) The Mechanics said you could tell that these pneumatic duct seals were really old. 4) What are the consequences if a failure of an old seal occurs at a critical time; e.g. already in an emergency situation and your down to HMG operation over the Atlantic or South America where airports are few? 5) Another incident like this can cost the company a lot more money. Seems to me in the interest of safety and long term company cost of a failure at the wrong time; that all old duct seals should be replaced on all 767-300 aircraft.

Data retrieved from NASA's ASRS site as of April 2012 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.