Aspirated TAT on the ground
Thread Starter
Join Date: Sep 1999
Location: ME
Posts: 5,502
Likes: 0
Received 0 Likes
on
0 Posts
Aspirated TAT on the ground
Having a discussion regarding the use of the aspirated TAT guage as a means of obtaining OAT on the ground.
Considering the heat generated off the gound, sitting in direct sunlight or even the exhaust heat from ground power trucks/air conditioning trucks.
At what point would you consider the TAT to be accurate?
Rgds.
Mutt
Considering the heat generated off the gound, sitting in direct sunlight or even the exhaust heat from ground power trucks/air conditioning trucks.
At what point would you consider the TAT to be accurate?
Rgds.
Mutt
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
The 'true' BA 737-400s had this and it was pretty reliable. If you are dubious at all I would say that certainly once you got moving off stand it was as good as a met observation.
Join Date: Oct 2003
Location: California (Highway Patrol)
Posts: 76
Likes: 0
Received 0 Likes
on
0 Posts
On the 'bus, I wouldnt trust the TAT gauge on the ground. I think an approximation for OAT can be made by looking at the SAT and taking 2 deg of the indication.
FP
FP
Join Date: Apr 2000
Location: BC
Posts: 450
Likes: 0
Received 0 Likes
on
0 Posts
Aspirated TAT
Originally Posted by mutt
Having a discussion regarding the use of the aspirated TAT guage as a means of obtaining OAT on the ground.
Considering the heat generated off the gound, sitting in direct sunlight or even the exhaust heat from ground power trucks/air conditioning trucks.
At what point would you consider the TAT to be accurate?
Rgds.
Mutt
Considering the heat generated off the gound, sitting in direct sunlight or even the exhaust heat from ground power trucks/air conditioning trucks.
At what point would you consider the TAT to be accurate?
Rgds.
Mutt
Join Date: Mar 2001
Posts: 66
Likes: 0
Received 0 Likes
on
0 Posts
B767 and 757
TAT measured by probe that is continualy deice by bleed air, on the ground this is unreliable as no or lack of airflow. This is why eng anti ice temp requirements are based on OAT on the ground(ATIS) and TAT/SAT in flight EICAS/CDU
TAT measured by probe that is continualy deice by bleed air, on the ground this is unreliable as no or lack of airflow. This is why eng anti ice temp requirements are based on OAT on the ground(ATIS) and TAT/SAT in flight EICAS/CDU
Join Date: Jun 2005
Location: NY
Posts: 278
Likes: 0
Received 0 Likes
on
0 Posts
Mutt, the Triple Seven sounds truly amazing 
doesn't reflection of heat off of a hot ramp cause some deviation? i.e TAT = SAT
How exactly are OAT temperature measurements taken... is this standardized?
doesn't reflection of heat off of a hot ramp cause some deviation? i.e TAT = SAT
How exactly are OAT temperature measurements taken... is this standardized?
Last edited by rhovsquared; 26th Jun 2006 at 20:32.
Thread Starter
Join Date: Sep 1999
Location: ME
Posts: 5,502
Likes: 0
Received 0 Likes
on
0 Posts
Not really talking about the 777... more interested in the antique B747 
rhovsquared
Thats the problem, with summer temperatures getting close to 50°C and where temperatures can rise 10° in 1 hour, the use of the old ATIS isnt reliable. As the aircraft has an aspirated TAT system, it needs airflow. Question is, how reliable is it without that airflow.
Met measurements should be taken by the aerodrome met office in a standardized way.
Mutt
rhovsquared
Thats the problem, with summer temperatures getting close to 50°C and where temperatures can rise 10° in 1 hour, the use of the old ATIS isnt reliable. As the aircraft has an aspirated TAT system, it needs airflow. Question is, how reliable is it without that airflow.
Met measurements should be taken by the aerodrome met office in a standardized way.
Mutt
Join Date: Jun 2005
Location: NY
Posts: 278
Likes: 0
Received 0 Likes
on
0 Posts
Mutt, I should read more carefully 
... that is a quite quandry, maybe a cross check during taxi where may TAT aproximates SAT approximates OAT, but then the TO data is already set and decided, I suppose 
Thank God I have no such choice, ATIS it is, but then again I don't have the lives of 421 pax and a multimillion dollar machine, that can cause billions in damage, to worry about
Ah, the -747- is and alway will be the Queen of the Skies, what a Lady
rhovsquared
Edited: to say the Phrase "should be taken ... standardized way" the should scares me, but alway very conservative ...
John Tullamarine, I heard you loud and clear, especially with General Aviation props... you won't see me at night, in the winter, flying IFR or VFR in the Rockies
even better the thermometer attached to the wooden post .along with the windsock but I love it.
... that is a quite quandry, maybe a cross check during taxi where may TAT aproximates SAT approximates OAT, but then the TO data is already set and decided, I suppose Thank God I have no such choice, ATIS it is, but then again I don't have the lives of 421 pax and a multimillion dollar machine, that can cause billions in damage, to worry about
Ah, the -747- is and alway will be the Queen of the Skies, what a Lady
rhovsquared
Edited: to say the Phrase "should be taken ... standardized way" the should scares me, but alway very conservative ...
John Tullamarine, I heard you loud and clear, especially with General Aviation props... you won't see me at night, in the winter, flying IFR or VFR in the Rockies
even better the thermometer attached to the wooden post .along with the windsock but I love it.
Last edited by rhovsquared; 28th Jun 2006 at 03:03.
