Intersection Takeoff Rules
 

Under the new rules for questions I think this belongs here not in Tech Log.

Can anyone point me at the place in the regulations (or advisory material) that specifies the manner in which an intersection takeoff is assessed for distance and slope. It seems logical that for an intersection takeoff, I pretend that the runway behind me doesn't exist, and I use the slope and distance for the runway in front of me for performance purposes. But a quick scan through the FARs keeps turning up the phrase "length of the runway" without (apaprently) defining it as "length of the runway in front of me". Similarly the landing regs keep mentioning "effective length" and I can't find any specifics for that term either.

Any help gratefully received - trying to find a regulatory justification for the common-sense approach.

Obviously, YOU will have to determine the length and condition of the runway in front of you, and disregard any runway you decide to leave behind.

When it comes down to reality, FAR 91.13(a) rules here, AND will be the first rule cited in any violation hearing:
While 91.103 addresses the need to "become familiar with all available information concerning" the airport, runways, and airplane performance, it does not tell you what to do with that information. So, as long as the runway remaining is more than that required by your performance charts/tables AND you don't crash or generate a noise complaint, you won't get a violation. HOWEVER, if ANYTHING goes wrong that generates the interest of the feds, one of the first questions asked will be why you didn't use the ENTIRE available runway.

You could also use (and extend) the advice of AIM 5-1-2.a -- "To maintain IFR proficiency, pilots are urged to practice IFR procedures whenever possible, even when operating VFR." Check out the relevant paragraphs in Part 121 (121.177, .188, .188, .196...). Use the [15%] runway additives for wet runways, etc, even when operating VFR. You can then, at least, show that you understand the rules and attempt to use a reasonable margin -- the same as those used in commercial operations -- in your planning.

The Old Adage...
 

Runway behind you and fuel in the bowzer is no good to you. Also, with the ability to operate with 'De-rated' engines and utilizing Assumed Temperature calculations together, is looking for trouble. It doesn't matter if the performance fits.
There seems to be a missing element in the pilot group today and that's called:

AIRMANSHIP

As Commander and even as a good assertive CRM savvy Co-Pilot, the responsibility for the conduct of a safe flight rests in your hands. Forget what the company wants you to do. The beginning of the operations manual Part A, (if written correctly) tells the reader that the Commander has the sole responsibility for the safe operation of his/her aircraft.

Thanks, SSG V10

I find the old rubbish of runway behind you, fuel in the bowser, sky beneath you rubbish from yesteryear, just that, rubbish from yesteryear. The modern world still requires airmanship and at times, because of the way modern systems work, maybe more than it did in years gone by. I'll return to that later.

Our Mad (Flt) Scientist has brought an important issue up. Slope affects the position relative of objects when airborne, especially those close in and knowing that these things have been taken into account by the Performance guys would be comforting. It is especially important if you depart from an intersection on a runway that starts with a downslope. Our company have assurances from those who supply our performance data that 1) Declared distances used are matched in the tables and 2) The (revised) slope is taken into account. We have been supplied with (generic) diagrams that show us the point on the runway where the declared distances are measured from. We also have data that gives a (very) conservative distance vs. weight penalty.

Returning to the rubbish. When you work for a reasonable company, you are not asked to fly outside the rules. You are not pressured to fly without sufficient fuel. You are not made to 'flex' every flight. And as a commander, together with your crew, you try to operate safely. That means sticking to the rules, following the performance charts and operating in accordance with SOP's. When these things let you down or you can see problems ahead, that's where the "Airmanship" kicks in. Take for example, intersection takeoffs. Is it always more dangerous to do them? Without more data, how can you know? I can tell you that the speeds will often be different and as such, the possibility of a 'reject' will vary, as will the chance of a tyre failure etc. And we haven't considered the tyre and brake heating up as Captain "Ultra Safe" taxies the extra kilometer to avoid the intersection take-off. And this "fuel in the bowser" rubbish. Knock yourself out if you wish and fill your plane up every flight - after all it's safer, isn't it? Obviously the extra weight won't increase the take-off speeds, reduce the climb rate, increase the landing speeds and distances required, or will it? So you'll just add a ton then? Is that just 5% safer or a full 10% safer?

Then we have de-rating/flexing etc. Safer or not? What is for sure is that you'll run cooler engines, reduce the chance of a failure, reduce VMCA and you'll still have Full Whack available if you need it. You'll also have an artificial weight penalty "to add a bit for mum and the kids."

Like most things, we have to make compromises. We make these compromises based on knowledge. Our job is therefore to trade economy for time and convenience - not safety. And safety is a shared responsibility for the regulator (eg. In Europe he knows we do flex. and intersection departures, he approved the figures and calculation methods), our companies, the manufactures and last of all, US!

Safe flying,

PM

PS: Good question Mad (Flt) Scientist

See the boy has come up in the world GF. Now driving a 777.