Intersection Departures

[Typhoon1244]

I'm having trouble finding anything about this in print: the tower wants to give you a takeoff from an intersection. You don't have data for that particular intersection, but you do have numbers for a more restrictive (shorter) intersection. Are you legal to take the intersection offered?

I always thought the answer was "yes," but I'm second-guessing myself.

Anyone?

 

[Skyboss]

If I remember correctly, it's an agreement between the facility and the FAA, or based on airline policy. I know of one airline that forbids such departures - SkyWest - or at least they did in 1995. I don't think it's a searchable item.

 

[Typhoon1244]

Thank you, Dr. Airport Management.

Now, can someone answer the question I asked?

 

[Skyboss]

I gave you a straight up answer...

 

[Gator1999]

If the runway analysis guarantees that you can maintain the required climb gradient for a takeoff from that intersection (most restrictive) with an engine inoperative at V1, then you are also guaranteed the required climb gradient for the departure segments for any intersection (less restrictive) further down the runway. So yes.

 

[Typhoon1244]

...yes.

I tbhought so. Thanks. Do you know if that's in writing somewhere?

Originally posted by Skyboss
I gave you a straight up answer...

Basically you told me that intersection departures are allowed. I know that. Gator answered my question.

 

[Gator1999]

Typhoon,
I know that it is in the runway analysis preface that we have at Mesaba. All of our runway analysis data comes from Jeppesen. Contact your fleet manager for the aircraft that you fly and I'm sure that they will be able to point you in the right direction, and hook you up with whatever you need. Hope it helps!

 

[Caveman]

No you aren't legal to take what appears to be a less restrictive intersection unless you have the numbers for that particular intersection. Remember, there is a lateral component to obstacle clearance and intermediate intersections may not provide the required lateral safety necessary to meet 121 requirements.

 

[Typhoon1244]

Gator1999: YES (according to Mesaba/Jeppesen runway analysis)
Caveman: NO

Anyone else?

 

[BJK]

For what it is worth, this was discussed in length at SkyWest a few months ago on our internal website. I'll have to check it again, but to my very best recollection, we have been told it is OK to depart from a less restrictive intersection when not listed on our performance analysis.

 

[enigma]

If you don't have data for a specific intersection, don't use it. Taking off from a less restrictive intersection may seem reasonable, but how do you prove it to be legal and safe? I don't know the answer to the original question, and since I can't say for sure, I most certainly wouldn't put my ticket on the line on a hunch.

I would call my POI and ask the question if I were really concerned about the situation. I will venture to say that he/she will also say that you don't use any intersection that you don't have data for.

Additionally, remember that your best chance of getting violated comes from situations where the FAA can point to something in writing and show that you didn't comply. You know what I mean. The have no real way to prove that you went fifty feet low, but they will find every addition mistake on your manually computed w&b. Same goes for take off data. They may not be able to prove that you took off after burning into your min fuel, but they will have no trouble proving that you took off without data.

regards,
enigma

 

[dispatchguy]

As an active 121 dispatcher, I would concur with Enigma.

If you dont have official numbers, just dont do it.

Now, if this is an intersection that ATC likes to use, have your ops engineering department get the data to generate a weights table for that intersection.

While it may make sense by using the numbers for a more restrictive intersection, what would you say to an inspector if you got ramped on arrival?

 

[Skyboss]

Basically you told me that intersection departures are allowed. I know that. Gator answered my question.

I assumed you were refering to the context of a carrier.

 

[dmspilot00]

There seems to be no reason why you can't takeoff from an intersection that is before an intersection that you have data for, but if in doubt why don't you just tell the tower you can takeoff from the more restrictive intersection? Or do a high-speed taxi from intersection A to B before applying takeoff power.

 

[transienttorque]

No you aren't legal to take what appears to be a less restrictive intersection unless you have the numbers for that particular intersection. Remember, there is a lateral component to obstacle clearance and intermediate intersections may not provide the required lateral safety necessary to meet 121 requirements.

I concur. Several check airmen have said the same thing.

Skyboss, save your breath for cooling pies.

 

[Skyboss]

Okay Mr. Super Pilot man!

 

[SSDD]

Basically, it depends on who did the engineering and the method that they used. Runway analysis is not straight line, it fans out from the takeoff point. The shape of the fan is such that an obstacle may come into play from the approach end of the runway, but not from an intersection, even though you have more runway available. To get the definitive answer, you'll have to ask your company's engineering dept, or your performance contractor.

Never an easy answer, is there?

 

[Typhoon1244]

Or do a high-speed taxi from intersection A to B before applying takeoff power.

I thought about that.

 

[Skyboss]

Runway analysis is not straight line, it fans out from the takeoff point. The shape of the fan is such that an obstacle may come into play from the approach end of the runway, but not from an intersection, even though you have more runway available.

More specifically, 7:1 going away and 20:1 on both sides of the RCL.

 

[skeezer]

At my company we are allowed to use a less restrictive intersection that we do not have numbers for. This is specifically stated in our manuals so there are no worries.

I guess it has to do with who your POI is and the exact method with which your takeoff data was generated.

Peace

Skeezer