An MD-83 on a maintenance test flight experienced a loss of pressurization and a failed antiskid system.
Synopsis
An MD-83 on a maintenance test flight experienced a loss of pressurization and a failed antiskid system.
Narrative
We were performing maintenance directed pressurization tests when the auto controller 1 and 2 failed. Soon after; the cabin altitude rose rapidly and we started a descent. Cabin altitude eventually got to around 25;000 FT. We descended with our Oxygen Masks on; coordinated with ATC; and performed applicable checklists; while heading back to our origin airport. On approach we put the gear down and received inboard/outboard left and right anti-skid failure. We communicated this to ATC and were granted the longest runway. We performed all applicable normal and abnormal checklists during this process. Landing was uneventful. Upon clearing the runway; we stopped the aircraft and coordinated for the fire trucks to perform a visual inspection. All looked good to them and we had normal indications in the flight deck; then we taxied to the ramp for shutdown.For this test flight; we had Maintenance in the jumpseat. Having him there was extremely helpful for our abnormal situation. We were able to get input from him and delegate some tasks. I recommend having Maintenance onboard for test flights.
Second reporter narrative
We arrived at aircraft to perform a maintenance check flight. During the preflight I found that the AUTO 1 and 2 controllers showed a fail light. As the aircraft had just had power applied I asked the Maintenance Tech about this. He responded that the test switch was probably out of position and he would go look at it. By the time I finished my walk around the system was working and I saw nothing wrong with it. I tested both systems thoroughly (via my normal pilot preflight) and they both worked with no issues. We climbed to FL330 to perform the single pack tests which involve turning off 1 pack and taking the other pack to HP BLD OFF (high-pressure bleed). During the test of the left pack system I noticed that the FLOW light did not illuminate when it should have (the cabin was climbing within test limits and the outflow valve was fully closed). I mentioned this to the onboard Maintenance Tech. After noting this; the AUTO 1 and AUTO 2 controller failed simultaneously. The outflow valve failed fully closed. I then began manual pressurization procedures. I was able to stabilize the cabin via manual pressurization and told the crew that the test was over since we now had a bigger issue. As we prepared to return to the airport and I continued to run manual pressurization; the cabin began to climb rapidly and I went into the EQRH procedure for rapid decompression. By the time I got to the first item on the checklist the cabin had already reached 14;000 FT and the CABIN ALT light and aural warning came on. I declared an emergency and informed ATC we were descending to 10;000 FT. We followed the checklist and began a descent. After reaching approximately 27;000 FT the cabin finally began to respond to the closed outflow valve. I was able to stabilize the cabin via manual pressurization and told the crew that the test was over since we now had a bigger issue. The cabin went from 8;000 FT to 25;000 FT in less than 2 minutes.As we were returning I knew we still might have an ANTI SKID problem so I brought the gear out early to check. The ANTI SKID fault on all four wheels returned. We ran the EQRH checklist again and it was not successful. I informed ATC of our new problem and requested the longest runway they had as well as to have the fire trucks out in case of any tire issues. We were light and; with the long runway; very minimal braking was used and therefore had no brake issues. We had the fire trucks do a visual inspection to be sure and then taxied into the ramp.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.