Terps & cold wx ops

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
Joined
Feb 23, 2005
Messages
20,334
Location
west Texas
Display Name
Display name:
Dave Taylor
Does approach/airway design include allowance for altitude variations that might come with very cold weather in the US?
This suggests for Canada that it might not, just wondering about here.
Ie in mountainous areas, mea is min. 2000' above terrain - the chart seems to suggest that in extremely cold weather you may be 500' true altitude above a 10000' peak in Colorado?
 
Dave,

I have not seen adjustments for temperature except for LNAV/VNAV approaches when using Baro-VNAV equipment. Since the Baro-VNAV equipment constructs a glidepath based on the sensed altitude at a given distance from the threshold, it is subject to altimeter errors caused by temperature. The approach charts will have both a minimum and a maximum temperature that Baro-VNAV equipped aircraft are authorized to fly a given approach.

The very same approach based on WAAS GPS does not have the same limitation, as only the glideslope in space is not dependant on the altimeter and the altimeter is only used to determine the DA, where the aircraft is close in altitude and distance from the barometric pressure sensor, usually on the ground at the airport. If an alternate altimeter setting is authorized, there is a corresponding increase in minimums that takes into account the added distance to the barometer setting equipment.
 
The answer is "no" -- published mins in the USA do not give any extra allowance for extra cold weather. You are responsible for making the necessary corrections per AIM Section 7-2-3 to which David provided the link above. The only difference with Canada is that the Canadians required their pilots to have that table in the cockpit under certain conditions.
 
We had that table with us everywhere we flew. We might land at Dutch Harbor. We might land in a typhoon. Looking back, it's amazing I lived.
 
You must log in or register to reply here.
Back
Top