A Complete Manual for Conducting International Flight Operations

Temperature Monitoring

ISA Temperature Monitoring

   While in cruise, particularly on routings that take the aircraft to Northern Latitudes, or when evaluating step climbs it is important to monitor ISA temperatures. As mentioned earlier temperatures may be significantly above ISA at Northern Latitudes. This is due to the tropopause being lower (altitude) the closer you get to the earth’s poles. The tropopause is lower because it receives less radiant heat from the sun and therefore less convection occurs. In the below example the ISA deviation jumps significantly between ETP 1 and 6430N. As a crewmember being aware of the forecast jump in ISA temperatures is essential because it is possible that crewmembers may decide to climb the aircraft prematurely and when the ISA deviation spikes aircraft limitations may be exceeded or the aircraft may not be capable of maintaining the given altitude and airspeed.

Hydraulic, Fuel, & Oil Temperature Monitoring

Prior to coasting out ACI Jet crewmembers shall evaluate aircraft system functionality and performance.

Hydraulic Temperature Monitoring

For Gulfstream type aircraft the hydraulic systems are continually pressurized at 3,000 psi and considering that the flight controls are manipulated using hydraulic pressure it is worthwhile evaluating the system functionality and fluid level prior to entering an isolated flight regime. For the G-IV the appropriate fluid level in flight would indicate that the combined fluid level is half-full and the flight side hydraulic system is full.


For flight crews unfamiliar with the hydraulic levels in flight this hydraulic  indication may

seem unusually low, but for this aircraft is appropriate. Knowing appropriate indications make it easy for crewmembers to identify hydraulic leaks or component failures before they become critical issues. Hydraulic systems on the Gulfstream are also dependent on heat exchangers which are located in the fuel tanks. Should a failure of the heat exchanger occur the hydraulic temperatures would rise and potentially cause failure of the system.

Fuel & Oil Temperature Monitoring

It is also advisable for ACI Jet crewmembers to monitor fuel and oil temperatures while in flight. All ACI Jet aircraft have fuel/oil heat exchangers, and provided the system is operating properly the fuel will be warmed and the oil will be cooled. ACI Jet crewmembers shall have a general awareness of what fuel and oil temperatures are considered normal at altitude and shall monitor the fuel and oil temperatures for any trend that would indicate a failure of a system component. ACI Jet crewmembers shall also consider the impact of CAS messages relating to fuel or oil systems such as oil/fuel bypass prior to coasting out and while oceanic.


Revision date: July 29, 2015

View Update Log


The material contained on this site is to be used for reference  only. You should always follow your primary resources first (aircraft manuals, government regulations, etc.).

Savant Aero is no way affiliated with any aircraft manufacturers.