2% Runway slope limitation

[bafanguy]

'Sled,


Ya, I figured other people might have to do this the hard way, but assumed the original questioner was a 121 guy.

So the 91 & 135 guys have to drag out those giant, virtually indecipherable graphs and do a runway analysis each time even if they're operating a Part 25 airplane ?


I've never operated in 135 or a pure 91 situation.

 

[A Squared]

While we're talking slope...

I used to fly a PT135 twin in and out of a dirt strip with a 6% grade. Can anyone top that?

We do charters with the DC-6 to a gold mine where the airstrip has an 8% grade. Also I've landed on a glacier on Denali. I have no idea what the grade is, but I had climb power on touchdown

 

[HMR]

We do charters with the DC-6 to a gold mine where the airstrip has an 8% grade. Also I've landed on a glacier on Denali. I have no idea what the grade is, but I had climb power on touchdown

8%!!!
While we're on the subject of calculating percentages: You're probably a 100% better pilot (no really, you fly a DC-6 to a gold mine, I fly a jet for a guy with a "gold mine"), minus the difference in the runway slopes (8%-6%)... That equals my T/O's and landings being 98% more impressive.

 

[Lead Sled]

I figured other people might have to do this the hard way, but assumed the original questioner was a 121 guy.

I admit, I misread his information. I assumed that he was a 91 or 135 guy. I see that he's flying an Airbus. Your point is well taken, however I still would argue that knowing how to calculate a runway slope and the effect that slope has on takeoff performance isn't a bad thing - even if you've got an office full of folks and the latest and greated performance software to spoon feed the information to the crew.

So the 91 & 135 guys have to drag out those giant, virtually indecipherable graphs and do a runway analysis each time even if they're operating a Part 25 airplane?

Yep, that's correct. In the real world it can be done pretty haphazzardly and when you're operating out of an airport like Aspen (KASE) where it's pretty critical most guys aren't really up to it. There are a lot of misconceptions floating around and guys confuse the DP climb gradients and the FAR Part 25 mandated takeoff flight path obstacle clearance requirements. There was a good thread that touched on this a few days ago.

Luckily, there are computer programs available to make it easier for us poor slobs who have to fend for ourselves. Personally, I know how to do it "by hand" using the charts, but in the real world I do it just often enough to be a real hazzard - just like 98% of all of the pilots out there.

'Sled

 

[bafanguy]

'Sled,


Personally, there times when the "spoon feeding" is a lot better than anything I could come up with sitting in the cockpit juggling a pile of graphs and pushing a no.2 pencil. The more critical the performance parameters, the more important the answer to the puzzle is.

My old Douglas DC9 manual has a huge number of those graphs that are totally useless in the real world...can't imagine why they're in there as we weren't allowed to use them. Performance on the -9 in the summer was an eye-opener on heavy, Flap 5 takeoffs ( at one company, we made slats-only TO's ). V1 often happened in the hash marks on the departure end. Stop, even from V1-10kts...no one thought we could.

There are just too many variables that can't be controlled/relied upon to assume the end numbers are a scientific answer. But, one has to use the best/most accurate data available.


But, people just do what they have to do to keep things moving. It's a fun subject.

 

[Lead Sled]

I understand what you're saying. I'm all in favor of being spoon fed, the problem is that the Feds have mandated that 121 operators have someone to handle the airport analysis chores. You also have dispatchers that have a certain amount of decision making capabilities. When it comes to 135 and 91 operations, most dispatchers are little more than scheduling secretaries. You hit the nail on the head when you said that "people just do what they have to do to keep things moving."

'Sled

 

[bafanguy]

I understand what you're saying. I'm all in favor of being spoon fed, the problem is that the Feds have mandated that 121 operators have someone to handle the airport analysis chores. You also have dispatchers that have a certain amount of decision making capabilities. When it comes to 135 and 91 operations, most dispatchers are little more than scheduling secretaries. You hit the nail on the head when you said that "people just do what they have to do to keep things moving."

'Sled

'Sled,

I agree. However, where dispatchers are concerned, their decision making ends at the point where the captain signs the release...or he doesn't. There is a mistaken notion that airline guys just tear the flight plan off the printer and go. Nothing could be further from the truth. I looked at dispatchers, in the practical, every day sense, as providers of information...and backup. I was the one with his hand on the parking brake lever...not the dispatcher...and the CP's office would back you to the hilt.

I could tell you stories...

 

[JAFI]

I got into this discussion late but, here are my 2cents.

The run over rise calculation is correct and it is in percent of 100.

2% in not (I believe) a certification issue. If you look at performance charts that cover over 2% you will see a big drop in performance (at least up hill). So it may not be so arbitrary. Many aircraft are sold with the 2% as a limitation. The aircraft can operate above 2%, but you have to pay extra for the charts, a lot extra. For some aircraft you can also get charts for a take off altitude of over 8000’ (or what ever the limitation is for that aircraft) and over 120 degrees F but they can also cost extra. I have seen large turbojets with STC jado rockets in the belly for engine failure take off performance boost above 8000" high airports.



Every pilot has to take runway slope into the performance calculation (see 91.103 b2 Preflight Action) and the 121/125/135 equivalent regulation. The air carriers have the performance done for the pilots to quickly determine how much weight they can take off with at what temperature. The part 91 and 135’s who dispatch themselves using the aircraft manufactures performance charts begin with a weight calculation and end up with runway distance. You can pay for a service to do the math for you.


During a type rating oral, aircraft performance is fair game. Some companies do much of the work for you so there is not much for the examiner to ask, and some companies or individuals do none so it is all fair game. Jepp charts do not publish runway slope on the chart but NOS does. The slope calculation is important if the operation or aircraft can or does go into airports that have slope concerns. The pilot should know how to calculate performance numbers. You can't always take off down hill (wind/traffic/obstructions/departure procedure/etc.) so the pilot needs to know what the aircraft performance limitations are.

The dip or rise in the runway is not part of the slope calculation. I remember that if the runway is over 8000’ then the dip/rise is figured in but I would have to look for the reference.

One last thing. Not all runways (usually small, poor airports) have the runway end altitudes published because they never did the survey or published the information. So you may not always have slope information. Talk about a real gotcha...

JAFI

 

[Lead Sled]

However, where dispatchers are concerned, their decision making ends at the point where the captain signs the release...or he doesn't. There is a mistaken notion that airline guys just tear the flight plan off the printer and go. Nothing could be further from the truth. I looked at dispatchers, in the practical, every day sense, as providers of information...and backup. I was the one with his hand on the parking brake lever...not the dispatcher...and the CP's office would back you to the hilt. I could tell you stories...

I understand that - I've had to deal with dispatchers who felt they had contol of the parking brake lever as well. The point I was trying to make is that 91/135 flying is typically more "hands on" when it comes to all aspects of pre-flight planning. By the way, we would all love to hear your stories.

'Sled

 

[C77MD80]

If you want to know the actual slope, check the afd (green noaa book) published every 56 days, it has the slope everywhere. Your AFM limitations and performance numbers are the limitations when you figure slope and conditions.

Hey dale, that's a great idea but I haven't seen an AFD in 10 years. We have separate company pages with all of our pertinent information.

Why the 2% limit. I've been on a few runways with slope, works just fine, take off downhill, land uphill, some of them are short enough it would be tougher getting in if it weren't for all that slope.

Good question MT, I'm sure the engineers have their reasons. Ypu gotta start somewhere....



BaFan, your absolutely dead on. I'm not sure why he is asking, none of the airports we serve as a destination, provisional, refueling or alternate even come close to 2%. I thought it would be nice to get brownie points though

The problem is that it's only the 121 guys that have someone doing this for them. The rest of us 91 and 135 guys have to fend for ourselves and do "our version of runway/airport analysis". He needs to know how to calculate slope and he needs to know how slope factors into the runway performance calculations. It's a fair question.



'Sled

Sorry you have to go through all that on your own. I think I would go crazy if I had to go through all of the spaghetti charts when in fact there are much easier programs figured out by computer geeks. I think the best easy way is to wag it part 91 if you are so fortunate.

Your right though, it is fair game and that's why I,m asking...