Good News for SWA Pilots!!!??? Breaking News?

[Oakum_Boy]

You crack me up. Why don't you answer both if you know? Or better yet just the important one.

It makes a big difference, that's why. The SWA pilots were (I'd bet my life on it) using actual landing distance numbers. Those "actual" distance numbers
are published in the AFM for contaminated runways. They take into account reverse.

Factored landing distance is calculated using no reverse on a dry runway. The FAA says you must [be able to] land within 60% of the available pavement at your destination. Plus 15% on a runway 15% longer if the runway is wet. The wet factored data includes reverse. These are planning numbers only used for dispatch.

 

[Lampshade]

It makes a big difference, that's why. The SWA pilots were (I'd bet my life on it) using actual landing distance numbers. Those actual distance numbers are published in the AFM for contaminated runways. They take into account reverse. Factored landing distance is calculated using no reverse on a dry runway. The FAA says you must [be able to] land within 60% of the available pavement at your destination. Plus 15% on a runway 15% longer if the runway is wet. The wet factored data includes reverse. These are planning numbers only used for dispatch.

I don't know why you're betting your life on them using ALD? Do you really think that they are going to call dispatch up on every landing looking for FLD? lol It's been dispatched there, the consideration has been done. ALD is the important one once airborne. If TR are taken into account what is the adjustment if they don't work? i.e. spoilers fault x1.3, anti skid x1.5, auto brakes x1.2 If you don't fly the 737-700 don't reply. thank you

 

[Oakum_Boy]

I don't know why you're betting your life on them using ALD? Do you really think that they are going to call dispatch up on every landing looking for FLD? lol It's been dispatched there, the consideration has been done. ALD is the important one once airborne. If TR are taken into account what is the adjustment if they don't work? i.e. spoilers fault x1.3, anti skid x1.5, auto brakes x1.2 If you don't fly the 737-700 don't reply. thank you

They were using ALD that considered T/R, that will come out in the findings. My point was, that the only numbers that don't consider reverse, would be the dry FLD. Those, obviously, are not of use when airborne. I would be curious to see Airbus numbers for a contaminated runway. They must be rather restrictive if not considering reverse, no?

 

[Lampshade]

They were using ALD that considered T/R, that will come out in the findings. My point was, that the only numbers that don't consider reverse, would be the dry FLD. Those, obviously, are not of use when airborne. I would be curious to see Airbus numbers for a contaminated runway. They must be rather restrictive if not considering reverse, no?

Care to comment on this: The -700 OPC landing module computes a deceleration rate as a combination of reversers and brakes. (-300/-500) The OPC computes landing performance based on ‘brakes only’ deceleration. Actual braking performance using brakes and thrust reversers will decrease computed landing distance. As far as the Airbus numbers they are not unusually different from any other plane that I have flown.

 

[GVFlyer]

Part 25 is not of consequence only to test pilots during certification.

If you look in the limitations section of a transport category aircraft's AOH, I suspect you will see Part 25 mentioned as a basis for the data. Part 25 regulations are used along with Part 121 regulations in governing the daily operation of an airliner.

A good way to think about it is: Part 121 tells you how much runway is required, and Part 25 tells you how much runway is actually used.

You are correct in assuming that you should go to the Aircraft Flight Manual for take-off and landing data. That information is required to be certificated data, however, the methodology we use to provide that data is inappropriate for your use. For instance all landing data derived for GV certification was accomplished with 95% worn brakes at weights up to 91,000 lbs. V1 data was determined by actually canning engines at V1 at MGTOW. Mmo at M 0.885 was derived by accelerating the aircraft until we encountered a rudder control reversal at M 0.955.

Cruise manual data, by the way, is not certificated data and is required only to be indicative of a test article in the certification program.

Even as a manufacturer, when assisting a major customer in developing Terrain Critical High Altitude Special Procedures, we were required to use FAR Part 121.189 and Far Part 135.379 as we were developing operational standards, not seeking aircraft certification.

GV

 

[Dumbledore]

I see. So what you're telling me is that I can land at Ref +30 using takeoff flaps, and use only reverse to save the brakes, and I'll use exactly the amount of runway it states in the performance charts?

Where do you think your takeoff and landing data comes from?

You just don't get it, do you? What on earth are you talking about?

Look, Part 25 governs aircraft manufacturers. That's it. End of story. Part 121 governs scheduled air carriers and thus, to a certain extent, it governs pilots. That's that. End of story. The two have NOTHING to do with one another.

As for where the landing data comes from, that comes from the AFM as far as the pilot is concerned. Again, Part 25 has ABSOLUTELY NOTHING to do with it. The reason it's there in the AFM in the first place has EVERYTHING to do with Part 25. It's there because part 25 says the manufacturers have to gather the data and publish it for the pilots' use in the AFM.

 

[Dumbledore]

Not on a dry runway, I'm afraid. You're saying that two buckets are more effective than one? That isn't rocket science. My point is that on a dry runway, thrust reverse has relatively little importance when comared to a slippery runway. One bucket or four, it is all relative-

Agreed - sort of - but, you're ignoring my point. Reverse effectiveness is aircraft specific. You started out saying that reverse thrust is less effective on a dry runway and that reverse effectiveness is predicated on runway assumptions. That's not true. Reverse thrust effectiveness is based FIRST on how well it works in the installation concerned!

I've flown a number of jet types and each is unique in the way it reacts to the application of max reverese thrustfor stopping. Some reverser installations are indeed EXTREMELY effective. For example, landing a G-III on a 5000' runway with a Vref of 123 kts, I didn't need to even touch the brakes until I started coming out of reverse at 70 kts and I had about 1500' to spare. a G-IV doesn't perform nearly as well.

 

[Wankel7]

While I certainly don't want to offend anyone, I keep reading and hearing that the landing was "smooth". I just landed my Falcon 20 in blowing snow during the same storm when it hit the northeast on Friday. AND on a runway that's 4840'. Understand, my airplane only weighed 26,000 #'s (I have no idea 737 data), but by landing "firm", I was able to deploy the TR's without any hesitation and barely touch the brakes (didn't want to crank them up on a contaminated rwy), leaving about 1000' remaining. I can tell you when I give the customer a smooth landing, the squat switch doesn't always engage immediately. I don't want to speculate on another pilot's technique, however I am saying what my experience has shown me. During the winter in the northeast, sometimes an ugly "carrier" landing is all I can give 'em if the runway precludes the much sought after grease.

Your DA20 has TR....lucky Good call on just getting it down. Not a time to be screwing around.

 

[9GClub]

See below. =)

 

[9GClub]

Yes, absolutely! Thrust reversers have negligible effect on a dry runway!
Surprised? Well, hopefully you're not equally surprised that on a wet runway, the coefficient of friction (mu) is diminished. Brakes are effective, but not nearly so as thrust reversers. As friction decreases, so does the effectiveness of the brakes. Therefore, thrust reverse becomes more effective than brakes!

Wet and contaminated landing distances are calculated using thrust reverse as well as brakes. It may seem illogical, but you have to consider more complex issues on transport certified aircraft.

Lesson over.

It's only illogical in the sense that if your TRs aren't working, you're screwed. Of course TR is more critical (proportionally relative to braking) on a dry runway, but we're not dealing with a dry runway. We're dealing with a short, slick runway and a tailwind. My point is that there's not enough margin factored into the numbers to preclude a not-so-happy outcome in the event that something breaks. Of course it's not possible to plan for every contingency, but c'mon. Crappy weather, a tight field, and sucky runway condition/orientation? I don't care what kinda pilot you are.

Not trying to be arrogant guys, I prolly woulda smashed through the fence too. In my 150. Just sayin'.

My low time and apparent global ignorance aside, however, does anybody wanna humor me and agree that 31C that night was an accident waiting to happen?