How do you calculate your 3 degree Decent on an ILS approach or GPS approach and decide which Feet Per Minute To Decent how to calculate it? Help Please I Crash every Single time On ILS and GPS approach
I Don’t know which category to put so I put in General.
On an ILS or GPS approach which has a 3 degree glideslope,
-You should at 3,000 feet 9 nautical miles from the runway
-If your speed is around 150 knots, your descent rate should be around -800 fpm
I found this on the community. I’ve ever heard about this but can’t find it. Maybe this is relevant.
Follow the glideslope in your approach.
Rules of thumb - 3 X your height in thousands gives you range and 5 X (or half) your ground speed gives you height.
Eg. 3000 X 3 = 9 miles
GS 150 X 5 = 750 fpm (150/2 = 75)
If you are properly on the top of the ILS GPS marker:
- you should be 3000ft AGL from the touch Down Zone (TDZ)
- you will also be 9nm out from the TDZ
At this point if you are in Airbus A320s B 737’s (in other AC this speed will be different)
- you should be at 160 kts KIAS
Your descent rate should be 1/2 your speed and add a zero
ie 160 x 1/2 = 80 and add 0 so descend at 800 ftpm
As you get closer to the TDZ you will be decreasing your KIAS to get to 135-140 KIAS on TD (assuming no wind factor). Keep your descent rate using the same calculation as above
- 1/2 KIAS and add a 0 on entire approach
Keep checking your instruments to see you are properly on the glide slope
THIS IS A THING TO KEEP IN MIND!
On the glideslope:
- use the pitch of the AC to adjust your speed: ie if you are too fast pitch the AC up if you are too slow pitch the AC down
- use power (throttle) to adjust height: ie. if you are too high on the glideslope reduce throttle to get back down and if you are too low increase throttle to get back up
- remember gentle does it better and do not make radical adjustments for both the above
Then there is the round out, which begins below 50ft AGL; and flare, which begins at just about 10ft AGL. At TD time your descent rate should be around 100 - 200 ftpm; but this is another topic!
Practice makes perfect.
Can we see degrees from the HUD?
@anon58665202… The HUD has 10 degree graduation lines above and below the Bullseye/artificial horizon/lubber line. Extrapolate 3deg Down on an eyeball approach. Touch down is 2 step, “Round Out” then “Flare”. Watch an auto land in a bus, on Speed, 3deg on glide slope, Decision Height, Retard throttle call, Round-out, Flare, Touch Down, Reversers, Taxi Speed, exit active. Max
Hopefully this will help as well. Stop crashing our beautiful planes lol.
if you look at the approach chart you will see the recommended glide slope (most of the time it is three degrees but varies) and you want to descent rate to be five times greater than your speed for a three degree.
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