Perf A - "Visual" Departures
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Perf A - "Visual" Departures
Have been told by a pilot of a UK operator which shall remain nameless (but they fly big shiny jets) that their operator has stated that if it is "visual" they can use alternative performance data which ignores the obstacle clearance criteria of Perf A.
Needless to say on certain runways at certain airfields this gives a considerable increase to the RTOW.
I recall that the CAA banned this practice in the early 80's - is it now allowed on JARs then?
It is not a practice that I would be at all happy with - the thought of climbing after take off with an engine out and looking out the window for the "obstacles" frightens me!
Anyone care to comment?
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Needless to say on certain runways at certain airfields this gives a considerable increase to the RTOW.
I recall that the CAA banned this practice in the early 80's - is it now allowed on JARs then?
It is not a practice that I would be at all happy with - the thought of climbing after take off with an engine out and looking out the window for the "obstacles" frightens me!
Anyone care to comment?
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The idea of avoiding obstacles by looking out of the window sounds exceptionally sensible to me, but I would be very wary of using 'alternative' performance data. The obstacle is only avoided vertically by 35' using normal data, so seeing it may not help very much!
It would depend if the limiting obstacle was a tower on the edge of the splay, or a ridgeline running across the take-off path. The first you could see & avoid, the second you just watch getting bigger!
Mt company requires that the obstacles be taken into account for all take-offs, yet special procedures may be discontinued in VFR once the Captain is assured of obstacle clearance. When that assurance is reached depends upon the type of obstacle, as above, and provides for some interesting VFR take-off safety briefs.
[This message has been edited by Checkboard (edited 06 April 2001).]
Mt company requires that the obstacles be taken into account for all take-offs, yet special procedures may be discontinued in VFR once the Captain is assured of obstacle clearance. When that assurance is reached depends upon the type of obstacle, as above, and provides for some interesting VFR take-off safety briefs.
[This message has been edited by Checkboard (edited 06 April 2001).]
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Some, and I say again some pilots in my company seem to think they can invent their own performance shedule. 2 things I hate: "we are VMC so don't worry about climb performance" I mean hello, am I missing something here? Do clouds have some sort of braking effect on aircraft? The only difference in VMC is that you will see the mountain you're flying into!
and: "I know performance tells us to accel at 1500 feet but we'll accelerate at eeeem, now lets see (guess guess guess) oh, 400 feet." So in other words we don't have a clue if we'll avoid obstacles or not but "I've been doing this for 25 years and nothing ever happened to me." Sorry to react so strongly, but I think it is something grossly unproffessional. Nobody 's perfect!
and: "I know performance tells us to accel at 1500 feet but we'll accelerate at eeeem, now lets see (guess guess guess) oh, 400 feet." So in other words we don't have a clue if we'll avoid obstacles or not but "I've been doing this for 25 years and nothing ever happened to me." Sorry to react so strongly, but I think it is something grossly unproffessional. Nobody 's perfect!
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Frederic and Oxford1G - I could not agree with you more!
A little bit of (UK) history would not go amiss here.
When Orion Airways started operating in 1980, many of the "procedures" were lifted from another leading charter company which shall remain nameless since quite a few the pilots who set up the Orion operation were from that company!
At CFU "Visual" RTOWs were published.
Not long after this BA (Airtours) started operating to CFU and could not understand why they were tech stopping for fuel on the way back to the UK but other operators were not.
CAAs attention was drawn to this fact and they investigated and promptly banned the use of "visual" RTOWs.
Have the goalposts changed again?
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A little bit of (UK) history would not go amiss here.
When Orion Airways started operating in 1980, many of the "procedures" were lifted from another leading charter company which shall remain nameless since quite a few the pilots who set up the Orion operation were from that company!
At CFU "Visual" RTOWs were published.
Not long after this BA (Airtours) started operating to CFU and could not understand why they were tech stopping for fuel on the way back to the UK but other operators were not.
CAAs attention was drawn to this fact and they investigated and promptly banned the use of "visual" RTOWs.
Have the goalposts changed again?
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It is perfectly acceptable to have different takeoff charts based on a VMC departure and a IMC departure.
The difference in obstacles is the width of the obstacle cone. On a straight out departure the IMC (normal RTOW chart) has a half width of 600 m. For VMC departures the obstacle cone may be reduced to a half width of 300m.
You CANT invent your performance... if u dont have an RTOW with VMC clearly stated on it. Then u MUST takeoff using the noraml RTOW chart.
If u lose an engine, it doesn't make an arse difference if u can see the obstacle as u fly into it. Its still going to hurt.
However if itd 600 meters to your left, and ther is nothing to your right, then in VMC conditions, it is perfectly allowable. And it is clearly stated in JAR OPS.
rgds
O\Z
rgds
O/Z
The difference in obstacles is the width of the obstacle cone. On a straight out departure the IMC (normal RTOW chart) has a half width of 600 m. For VMC departures the obstacle cone may be reduced to a half width of 300m.
You CANT invent your performance... if u dont have an RTOW with VMC clearly stated on it. Then u MUST takeoff using the noraml RTOW chart.
If u lose an engine, it doesn't make an arse difference if u can see the obstacle as u fly into it. Its still going to hurt.
However if itd 600 meters to your left, and ther is nothing to your right, then in VMC conditions, it is perfectly allowable. And it is clearly stated in JAR OPS.
rgds
O\Z
rgds
O/Z
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Fireflybob.... bizarre as it seems i think O\ZON is spot on with his explanation. We too have different pages in performance manual for VMC departures, ACE03 springs to mind along with FNC05. Try this link to the JAR web site and see if it's as clear as mud.
http://www.jaa.nl/jar/jar/jar/jar.ops.1.495.htm
Cheers, Scally
ps. This is the main index, very useful
http://www.jaa.nl/jar/jar.html
http://www.jaa.nl/jar/jar/jar/jar.ops.1.495.htm
Cheers, Scally
ps. This is the main index, very useful
http://www.jaa.nl/jar/jar.html
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Clear as mud indeed!
Wouldn't it be great if one of our more talented members(not me then)could do an up to date, understandable book on the subject.
Fancy the job Bob?
PS Is the above book mainly FAA or would it be worth buying for its JAA content?
Wouldn't it be great if one of our more talented members(not me then)could do an up to date, understandable book on the subject.
Fancy the job Bob?
PS Is the above book mainly FAA or would it be worth buying for its JAA content?
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It doesn't matter what procedures anybody uses, as long as the performance is CALCULATED and makes logical sence! Take for example V1. I've seen it so often in Firenze (for those who've been there, I don't need to draw a picture), where some captains take their hand of the thrust levers long before V1 because their feeling says they won't be able to stop anymore. Yet they've never actually ever stopped and measured the distance before in reality. I understand performance can be quite critical at times, but it does work, otherwise aircraft would not be certificated. Airbus is working on a system that calculates, compares and displays your required acceleration against actual accelleration in real time. Should be pretty cool...
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Ah! Orion Airways, those were the days eh Bob? Anyhow, what staggered me then as it amazes me now, is how, with the nose in the air some 12-15 deg, you are supposed to be able to see anything in the take-off cone in front of you. Mmmmm. But as I recall that was the theory. Great theory!
