Hot weather effects on the bleed air detection system
Effectivity: Global Express/XRS/5000/5000GVFD/6000/5500/6500 aircraft
ATA: 36
By: Technical Services team Do you regularly operate your Global aircraft in hot weather?
As climate change continues to affect all of us and extreme temperatures become the norm, aircraft operators may need to adjust certain procedures to protect their aircraft.
Here, we discuss the possible effects of hot weather and clarify the limitations of the Global Express/XRS/5000/5000GVFD/6000/5500/6500 bleed leak detection system.
The above Global aircraft models cannot take off at temperatures greater than 50°C (122°F), as per the airplane flight manual (AFM) and the flight crew operating manual (FCOM).
Further, a more specific limitation is also present under AFM 02-08 1A and FCOM1 07-06 Hot Weather Operation: “Auxiliary Power Unit (APU) bleed extraction above 45°C (113°F) outside air temperature (OAT) for air conditioning operation is prohibited.”
These limitations are reviewed with crews during initial and recurrent training sessions.
When retrieving OAT in relation to these limits, Bombardier does not recommend referring to weather apps. This is because the tarmac surrounding the aircraft will radiate heat, causing higher temperatures in the immediate vicinity. Consequently, the OAT used for the APU bleed extraction limitation should be the one provided by your automatic terminal information system (ATIS) or from the aircraft’s air data system.
Operating outside the system’s designed limitations may create issues, especially in the aft equipment bay area. Most of the bleed detection elements in that area have a trigger point of 124°C (255°F).
Some bleed detection loops may reach their trigger point and cause L/R BLEED FAULT (Advisory) or L/R BLEED LEAK (Caution) messages to be posted on the engine indicating and crew alerting system (EICAS). Operators may have to modify their operations to prevent these nuisance messages and potential damage to the aircraft.
Operating the APU bleed extraction for air conditioning outside the designed limitations will result in a high amount of heat in the aft equipment bay and may have negative effects on many components.
Additionally, safety is a concern for maintenance personnel who must inspect the bleed detection loop installation or search for potential bleed air leaks inside the high-temperature aft equipment bay. Troubleshooting could be delayed until extreme conditions abate and dispatch may be prevented.
Bombardier encourages operators to seek alternatives that may better suit hot weather operations. Here are three possible options:
Use a ground air cart or engine bleed air for the air conditioning system when OAT is above 45°C (113°F);
Keep the aircraft in a cooler location until ready for start (hangar, covered tarmac).
Some airports are installing pre-conditioned air (PCA) systems to reduce noise, fuel consumption and CO2 emissions.