Obstructions

[readbackcorrect]

Anyone have a idea or more preferable legislative source to easily establish whether an object is an obstruction?

Im working with 1:50 take off and also approach slope
The object is 75m tall, 800m from the runway end.

1:50= 2%

75/800= 9.4%

So obvioulsy an obstruction as the climb gradient necessary is inexcess of the 2%.

Am i right to believe that that the object intrudes by 59m in height?

.02*800m= 16m Allowable yet our object is 75m tall

Comments please

[Old Smokey]

Every single pimple on the earth's surface which is above the runway elevation is an obstacle. It does not become an obstruction (i.e. something preventing flight) if the aircraft has the capability of clearing it, with all engines for a light aircraft, or with one engine inoperative for FAR 25 aircraft (or it's equivalent). If you cannot reduce your weight sufficiently to clear the obstacle, you have 3 options available -

(1) Reduce the Effective Operational Length (EOL) of the runway to the point where the aircraft can achieve the lesser climb gradient required, OR

(2) Carry out a turning procedure after takeoff to laterally clear the obstacle by the prescribed splays, OR

(3) Don't go.

If you're talking about a FAR 25 aircraft (or it's equivalent) and you can achieve 9.4% gradient with One Engine Inoperative, please let us know, I want to fly it!

Regards,

Old Smokey

[Spitoon]

The UK's CAP 168 (http://www.caa.co.uk/application.aspx?categoryid=33&pagetype=65&applicationid=11&mode=detail&id=232) describes the treatment of obstacles quite well. And it's pretty close to the ICAO rules on the topic.