2023-03 · NASA ASRS report 1995584
Air carrier flight crew reported exceeding gear down speed limitation due to a lack of details in the hot brake indication QRH procedure.
After pushback from the gate; we were advised to expect runway XXL for departure. We started up both engines and did before takeoff checklist at the gate to be ready for an immediate takeoff. As we were taxiing out; we were immediately given a takeoff. Runway change from XXL to XY. Taxi instructions were to go north on Taxiway 1; and then transit the terminal ramp via Taxiway 2 south on Taxiway 3 to runway XY. Well; Taxi north on Taxiway 1; we were advised to hold short for a aircraft departing runway XXL while simultaneously trying to turn; if our table height would be too high to transit below the bridge on the first terminal ramp. We were then instructed to take Taxiway 2; while the first officer was also working on new takeoff data for runway XY. We then move south on Taxiway 3 to runway XY. Taxiway 3 has a slight decline to the runway. In addition to the long taxi and the high pressure altitude; this led to a high rate temp situation in retrospect. Due to the high workload; this was not at top of mind. Upon reaching the runway tower; advised us that we were clear for takeoff. When we were retracting the landing gear; we were met with a hot brake temp switch icon; and ECAM message. As we receive this message; we were on the RNAV departure; heading westbound toward the mountains. The departure has an at or below crossing restriction at 10;000 feet at ZZZZZ. Immediately following that it has four at or above crossing restrictions to make sure that you easily cross the mountains. As we looked at the brake temperatures they were just at the threshold and most were below the 300 deg limitation. Given the congested airspace; and the high terrain the first officer and I elected to continue to climb and then lower the gear at flight level 260. During the climb the brake temperatures continue to decline. However; the HOT icon on the brake temperature switch continue to display. In order to extinguish the message the first officer and I decided to extend the landing gear and turn the brake fans on. After the hot icon was extinguished; we slowed down to 240 knots in order to retract the gear to comply with the VLO retraction limitation.After slowing to below 240; we began to notice that the low speed queue was exceeding 200 knots. Given our high altitude and excessive drag caused by the extended landing gear; I did not want to mess around with a potential performance issue at altitude over mountainous terrain and elected to put the gear up just under 240 knots. It has since come to my attention that the 240 knots was some measured speed away from the 0.53 MACH limitation and we exceeded that limitation.High altitude airport. Lack of situational awareness regarding brake temperatures. High altitude gear extension and retraction. Runway change. High terrain. Congested airspace. For starters; flying a high pressure; altitude in airports; requires more awareness to brake temperature monitoring. This would've probably been briefed had we anticipated a contingency of a longer taxi. However; we were advised a short taxi and so we neglected the effects of high pressure altitude have on our brakes temperatures. Perhaps a note for outbound aircraft could do well as a reminder to check temps before takeoff As we reviewed the QRH prior to commencing the checklist; it advised that we could delay landing gear attraction; if climb performance; and obstacle clearance permits. However; given our awareness of the crossing restrictions; the high terrain; and aircraft performance; we felt we could perform this checklist at a higher altitude. Perhaps a note highlighting the fact that Mach speeds will increase to a point that it will be difficult to retract the gear below the mach limitation might have been of some assistance. Maybe something like; at flight levels above FL230; gear retraction becomes difficult due to Mach limitation. Many limitations that have multiple speeds to comply with will specify whether the higher or lower limitation takes precedence with a phrase 'whichever is lower/higher.' With the absence of this phrase; it almost gives it the feeling of subjectivity. Maybe specifying would make it more clear in an abnormal situation.
We taxied from the ramp to runway XY. We had expected and briefed a much shorter taxi to XXL which ATC informed us was possible. But due to inbound traffic they made us go all the way to XY. I checked the brake temps before takeoff and they were all in the green. It was right before rotation I saw one brake on the right main gear switch to orange no the HOT indication illuminated. I delayed retracting the gear for 10-15 seconds to give them some more airflow. we had crossing traffic; ATC handover and crossing altitudes on the departure to make for the high terrain west of the airport; so I retracted the gear to ensure climb performance and focus on those other items. There was only 1 brake temp high and all the others were much cooler and well down in the green. We figured it was a faulty sensor on that wheel. We flew the departure with all the altitude constraints. Once we got out of the busiest area we discussed the brake temp. It was still reading 300 deg with the Hot light illuminated while all the rest of the gear were all indication the bottom of the temp range. Again we discussed it being a reading problem. We then decided to be certain the brake was cool that we would drop the gear. We figured at that altitude it would be very cold and the airstream would cool it quickly. We referenced the QRH for the procedure and followed the speeds. Below 270 we dropped them. We waited for several minutes for the brake temp indication do finally turn green even though it was below 280 deg. It finally cleared and we slowed to 240 to retract the gear. It was brought to my attention today that even though we followed the QRH speed of 240 for the retraction that we exceeded .53m. The cause of this error is the ambiguity in the QRH procedure. Usually speeds are defined for a procedure is indicated or Mach. If both are limiting then it is referenced as the high or the lower of Kias or Mach #. This procedure does to have any such reference. This QRH should have a note of verifying both speeds are met. It should expand on the effects of the procedure being done at altitude and the potential for missing the difference in speeds.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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