Death made simple
26th Mar 2009, 13:29
A popular question going around the flying school at the moment is: how do you adjust the MDA to meet the 2.5% missed approach gradient if you can only do say 1.7% one in op??
any help would be apprieciated, thanks
Old Smokey
26th Mar 2009, 20:29
First, calculate the distance from the Missed Approach Point to the Missed Approach Altitude. As it's based (in this case) upon a 2.5% Gradient, multiply the Altitude difference by 100/2.5, i.e. a factor of 40.
For example, if your MDA is 500 feet, and the Missed approach Altitude is 2000 feet, the difference is 1500 feet. Multiply this by 40.
Distance = 1500 X 40 = 60,000 feet.
You mentioned an actual Missed Approach Gradient of 1.7%, that's 0.8% degredation, so multiply the distance found by 0.8/100 to find the increase in MDA required.
MDA Increase = 60,000 X .8/100 = 480 feet.
Your "new" MDA is 500 + 480 = 980 feet.
The mathematics are not quite perfect, but simplified and slightly conservative, but not by much!
Regards,
Old Smokey