I use Flugprestansa to get the close in obstacles and use the SID gradient for the gradient.
From your own AFM
Flap retraction will be initiated at the most critical level-off height
while the aircraft accelerates to V SE. Upon reaching V SE, continue climbing with flaps retracted at Maximum Continuous Thrust until all of the other obstacles are cleared.
What your manual says is retract the flaps at the most critical level off height (once you are clear of close in obstacles you can retract the flaps - this is what your manual is saying). Once you have achieved Vse (regardless of height, I added that bit because the bloke that wrote the manual thought it was clear) you can retract the flaps because THERE ISNT A CRITICAL LEVEL OFF HEIGHT ANY MORE and continue climbing WITH THE FLAPS RETRACTED until all the other obstacles are cleared. You calculate the weight you can carry for the temperature you intend to take off at. You take off. When you have cleared the close in obstacles and acheived the flap retraction speed you can retract the flaps. Then you can keep climbing. Thats it. Not complicated. In your own manual.
The tough bit is getting hold of the obstacle information and making sure that database is correct - ie have notam'd cranes and tethered balloons and the like been accounted for. Generally, obstacles are under the SID gradient so you just don't care about them because you're going to be above them anyway.
From an FGP of EGTE
Obstacles included in calculation: (Height above runway end / Distance from brake release point)
Oa: 488 ft/6687 m Ob: 185 ft/3965 m Oc: 174 ft/3900 m Od: 112 ft/3320 m Oe: 124 ft/3495 m Of: 63 ft/2785 m
Og: 88 ft/3142 m Oh: 48 ft/2645 m Oi: 275 ft/5530 m Oj: 36 ft/2517 m Ok: 242 ft/5304 m Ol: 952 ft/17567 m
Broadly speaking they are sorted in gradient order although I have come across anomolies before. This could be because FGP seem to sort the order from the start of the take off roll - obviously we are interested in the gradient from the DER so theres a bit of maths to do to correct the order but in this case its pretty much correct and the first obstacle is the limiting one at 3.2%. So I can choose to WAT limit my aircraft to comply with 3.2% and take off and actually know that I will clear any obstacle by the required amount because I've already calculated that the climb increment gained by my actual take off point will give me the clearance required (TCI). I do this as a cross check of the FGP data which simply gives me a weight limit and a QNH correction. I asked FGP to provide their data in a datastring form before because I wanted to perform further analysis but apparently its propriety. Also I mentioned the gradient sorting anomaly and they chap said they hadn't noticed that before so maybe that will change in the future.
Thus I have a way to comply with an engine failure at any stage. Before V1, V1 and above up to V2, V2 up to V2+20, and V2+20 and beyond.
By the way, have you found the bit in your G4 manual that says "you cannot retract the flaps below 400 feet because you cannot and you just cannot and don't ask why, you just aren't allowed" yet?
didnt think so..
Last edited by tommoutrie; 24th Nov 2012 at 10:17.