ILS or GPS?

[jtrain609]

Question: when you guys talk about being within 400', is that factored (60%) or actual landing distance?

EDIT: I was wrong, it's actual while in flight, required for planning purposes. But the book says, and I'm paraphrasing here, that if braking action is less than good, or if you have reason to believe that braking action is less than good to use the required numbers.

 

[SteveC]

EDIT: I was wrong, it's actual while in flight, required for planning purposes. But the book says, and I'm paraphrasing here, that if braking action is less than good, or if you have reason to believe that braking action is less than good to use the required numbers.

Uh...wut?

 

[jtrain609]

Uh...wut?

Sorry, I should have translated that.

Actual landing numbers = the actual number of feet you'll chew up on landing.

Required landing numbers = factored numbers, at 66.7%.

So when you're doing preflight planning, the company will look at the required (factored) numbers for dispatch purposes.

When you're actually in flight, and looking up the data yourself, you should look at the actual numbers.

BUT, there's a caveat. If the braking action is reported below a certain level (good, in this case), OR if the captain believes that there is some reason that you need an additional margin in determining which numbers to use, then use the required (factored) numbers for an extra margin of safety.

Make more sense?

At a point, it's the book saying that it's your butt if something goes wrong because you didn't use the more conservative numbers.

 

[Kingairer]

I wouldve shot the GPS approach as well. With it being a 9 knot tailwind, and no one to tell you otherwise when you get closer (non towered) I would think the GPS to be the more conservative approach. The 170 will fly it like an ILS is LNAV/VNAV so its non issue, but take that away and I still think GPS was the way to go. You should be able to arrive at your points without a level off 'dive and drive' and your probibilty of breaking out prior to MDA was high. Your primary risk on the ILS in this situation is the runway length and condition. Dont have the chart in front of me but after the DThreashold your looking at about 6000 feet of landing distance on runway 20 not counting the subraction for the normal glidepath. Worse case scenario for landing with the ILS is , You have no breaking action or Pireps ahead of you since its Nontowered, no up to the second wind info (unless you want to listen to awos the whole time, could have wind increases prior to landing), and you float long cant stop and run off the end. Worse case for for GPS 2 is you dont break and go missed or miss your VDP point for normal decent to landing and go around. If the discussion was NDB w headwind vs ILS w Tailwind, i would have a different answer.

 

[Screaming_Emu]

I'd start with the GPS, if that didn't work and I had enough gas, then try the ILS with the caveat of if anything doesn't look right (floating) go around and go somewhere else. Just like landing on a short runway, don't go for any style points, just thump it in and get on the brakes.

 

[BobDDuck]

I'd start with the GPS, if that didn't work and I had enough gas, then try the ILS with the caveat of if anything doesn't look right (floating) go around and go somewhere else. Just like landing on a short runway, don't go for any style points, just thump it in and get on the brakes.

That's exactly what we did. But we got in on the GPS so we never had to try the ILS.

 

[dasleben]

If the discussion was NDB w headwind vs ILS w Tailwind, i would have a different answer.

Considering the tight margins on the tailwind runway, I'd personally still go for the NDB. Then again, we shoot NDB approaches LNAV/VNAV (though raw data NDB isn't exactly unsafe, either).

 

[Rocketman99]

TW+wet+nontowered+short=I'll take the GPS Plus, don't really get to do those all that often so always welcome something different.

 

[cmill]

I'd go with the gps. Depending on my experience with the airplane, I'm not sure I would have even attempted the ils. Just not worth taking the gamble with a 400ft margin of error.

Sent via smoke signal.

 

[Kingairer]

Considering the tight margins on the tailwind runway, I'd personally still go for the NDB. Then again, we shoot NDB approaches LNAV/VNAV (though raw data NDB isn't exactly unsafe, either).

Youre right...With a moving map, and ability to overlay, NDB would be a non event as well. We arent authorized for them so i havent shot one in ages. ....Having flash backs about shooting them in a 1970s 172 though..

 

[SpiceWeasel]

Sorry, I should have translated that.

Actual landing numbers = the actual number of feet you'll chew up on landing.

Required landing numbers = factored numbers, at 66.7%.

So when you're doing preflight planning, the company will look at the required (factored) numbers for dispatch purposes.

When you're actually in flight, and looking up the data yourself, you should look at the actual numbers.

BUT, there's a caveat. If the braking action is reported below a certain level (good, in this case), OR if the captain believes that there is some reason that you need an additional margin in determining which numbers to use, then use the required (factored) numbers for an extra margin of safety.

Make more sense?

At a point, it's the book saying that it's your butt if something goes wrong because you didn't use the more conservative numbers.

You guys still use manual calculations? When we use manual or world flight we still have to ensure required distance is < runway length when we send for landing data in cruise. It's almost as if "actual" is more a good to know number than anything else.

 

[cmill]

Considering the tight margins on the tailwind runway, I'd personally still go for the NDB. Then again, we shoot NDB approaches LNAV/VNAV (though raw data NDB isn't exactly unsafe, either).

Ndb might change my mind, if it was raw data. I had to shoot enough of them on the van to know that they don't get you to the runway, they get you to the general area of the airport.

Sent via smoke signal.

 

[jtrain609]

You guys still use manual calculations? When we use manual or world flight we still have to ensure required distance is < runway length when we send for landing data in cruise. It's almost as if "actual" is more a good to know number than anything else.

Everything is manual for us. I do the performance calculations myself before departure, spin a wheel for W&B, then look up the landing numbers.

We probably carry 50 pounds in books up front for this crap. The only thing that is electronic is the actual sending of the W&B to the company, after I input the data having manually computed it.

 

[SpiraMirabilis]

GPS with vertical guidance.

 

[MikeD]

Youre right...With a moving map, and ability to overlay, NDB would be a non event as well. We arent authorized for them so i havent shot one in ages. ....Having flash backs about shooting them in a 1970s 172 though..

You do realize how candyass the bolded part sounds?

 

[zmiller4]

Question: when you guys talk about being within 400', is that factored (60%) or actual landing distance?

For a CRJ, I can't imagine 6000' actual landing distance at sea level unless you were looking at antiskid issues as well.

6500' isn't necessarily short for the CRJ, but I'd go for the GPS at that length with those winds.

 

[deadstick]

Another thought about tailwinds...a 10 kt tailwind which takes the aircraft speed from 140 kts to 150 kts increases the kinetic energy by almost 15%. Seems like the 400 ft is significant.

 

[EDUC8-or]

GPS all day long. Prior to the FAF set the MDA and just exercise caution that you don't bust through the intermediate stepdown altitude between the FAF and MAP. You can actually follow the snowflake and the suggested descent rate on the MFD and you should be good to go. That would put you right at the VDP/PDP right on about a 3 degree descent and the airplane will be in a 700-800 FPM descent. If you continue to land the airplane is trimmed up in a descent, if not you just go around.

 

[jmreii]

Scenario:

Winds 010@9. 700 OVC 2SM RA

Landing at an uncontrolled field with an ILS to Runway 20 (with 200 and 1/2 mins) and a GPS to Runway 2 (with 600 and 1 1/4 mins).

Pertinent data (but not really legally controlling in this case):

-Max tailwind for the airframe is 10 knots.
-The runway is wet.
-The runway is "shortish" for the airframe in question.
-The GPS approach has a nasty stepdown fix that gives you about .2 miles to get from an intermediate altitude of 800 feet to the VDP (well, PDP actually) at the MDA of 600 feet while flying at a ref speed of 145 knots.
-There is only a REIL on 20 while 2 has full approach lights.

Do you take the headwind or the tailwind approach?

And just for reference this is KPGV.

I would have like some more information on runway lengths, type of aircraft because 145 knots is a high ref speed, any flaps? is this day or night? I have mainly used Garmin 530's and up with WAAS in which will set up a glideslope for you making those stepdowns a piece of cake. I am leaning toward runway 2.

 

[jtrain609]

If we're heavy, the EMB-145 can have ref speeds with full flaps (45 degrees) in the upper 130's, so 145 for a plane of a similar size sounds like the plane is heavy, but it isn't that much higher.