A Captain reports the cabin airflow in their DHC-8-200 aircraft was insufficient for high ambient temperature operations. Pilot notes that Maintenance did not have any quantifiable means to determine proper system operation regarding cabin temperature or duct output temperature.
Synopsis
A Captain reports the cabin airflow in their DHC-8-200 aircraft was insufficient for high ambient temperature operations. Pilot notes that Maintenance did not have any quantifiable means to determine proper system operation regarding cabin temperature or duct output temperature.
Narrative
While deadheading on this flight; I noticed from my seat; which was towards the front of the aircraft; that the airflow in the cabin was minimal while taxiing at a low power setting. Accepting this as typical; I assumed the cabin airflow strength would improve once the flight departed. This however; was not the case; and airflow actually became worse. The cabin temperatures rose to a point where most passengers were sweating visibly and had made some sort of statement regarding the cabin temperature to passengers around them. The Flight Attendant was also repeatedly making comments about the heat. Upon arrival we discussed the temperature with the crew leaving the aircraft - they remarked that they noticed no abnormalities from the flight deck. During a brief inspection of the cabin I found a significant amount of condensation forming on the Row 4-LEFT Passenger Service Unit (PSU). I assumed this was due to pooling cold air above the PSU's. We departed ZZZ and found the gasper vent airflow in the flight deck to be comparatively low to the rest of the fleet. Upon arrival; Dispatch and Maintenance Control were contacted. The write-up 'cabin airflow insufficient for high ambient temperature operations' was entered. I explained to the Maintenance Controller my observations and provided him with information regarding the forming condensation in Row 4. To my knowledge no 'Corrective Action' was taken on this aircraft to rectify the situation and the system was operationally (ops) checked as 'Normal'. There is no means on a Dash-8 to quantify cabin temperature or duct output temperature. While a small amount of system operation variance is normal; a set of limitations should be developed to measure cabin temperature and gasper and duct output temperature to determine the cooling effectiveness of the aircraft. When compared to ambient air temperature this information would be useful to the mechanics during troubleshooting. As of now there is no quantifiable means to determine proper system operation which commonly leads to these issues being cleared as 'ops checked good' or 'ops normal' or some other unsatisfactory 'corrective action.' This is not the first Dash-8 to experience cabin temperature issues; and others before it in the past two to three months have been written up repeatedly before going down for a significant length of time to fix a significant; and likely persistent issue with the air conditioning system (bad seals; faulty valves; etc.). Simple aircraft routing should not dictate when corrective action can be taken on these aircraft.
NASA callback
Reporter stated their DHC-8-200's do not have APU's and no cabin temperature gauge in the cockpit. All they have are the AUTO or Manual Mode selector. When cabin temperatures are high and in the AUTO Mode; they will select full cold. If that doesn't help they will then select Manual Mode full cold to try and get cooler cabin temperatures. The DHC-8-200's have only one ACM (Air Cycle Machine) with air supplied from each engine; dual bleed source to the ACM. On the gate; the Air Conditioning (A/C) carts provide a good flow of conditioned air. But when the A/C cart is removed and engines started; only the gasper fan may be running. Reporter stated he was scheduled to fly the same aircraft a different day and had to strongly emphasize to Maintenance he would not take the aircraft if Maintenance did not do better trouble shooting to correct the insufficient cabin cooling and low airflow. Maintenance was concerned about the amount of time a full system trouble shooting would take. His First Officer had also stuck his hand in one of the upper sidewall panel lap seams where there was cold condensation and found an eighteen inch gap in the flexible red tubing connection that supplies gasper fan air to the passenger PSU's. The red flexible tubing seems to have been separated when the sidewall panels were reinstalled at some point in time; preventing adequate flow of conditioned air to the PSU's.Reporter stated Maintenance did more trouble shooting overnight and found a gasket missing between the output side of the ACM and the connecting supply duct. As a result; only minimal cooling air was being supplied to the cabin system. After the missing gasket was replaced and the cabin sidewall flexible tubing reconnected; the aircraft became their best DHC-8 for cabin air flow and conditioned air.Reporter stated the continuing sign-offs of their logbook write-ups and lack of any 'real' corrective actions being accomplished by Maintenance is an ongoing concern.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.