30 knot tailwind on final
03-01-2007 | 05:04 AM
#11
Chief Jeppesen Updater
Joined: Oct 2005
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From: Executive Transport Driver
In essence, these guys were flying their approaches(not landings) in a diminishing tailwind. So, is it easier to go from a diminishing headwind or a diminishing tailwind. I'm not sure. Seems like with the diminishing tailwind you'd at least be adding power to keep a constant airspeed/glidepath. With a dimishing headwind, you'd be reducing power to stay on glideslope and airspeed. Wouldn't you be more likely to land fast or long with a diminishing headwind?
Lose a headwind and you're going to be pushing the power up to regain that airspeed. Lose a tailwind and your airspeed is going to jump up, requiring you to power back. Rapidly diminishing tailwinds can result in low power settings, high airspeed and high groundspeed. That in my book equates to long and fast landings.
Think of it like flying through a microburst- what happens when you lose your headwind flying through the center of the microburst- you have to power up... when you finally recover from the tailwinds (ie increasing headwinds) you have to power back.
Either way, the conditions that MEM_ATC describes aren't really favorable for any transport category aircraft, when switching directions results in a more stabilized approach over the course of the descent (even if the crosswind is the same direct crosswind at landing).
It's also worth noting that for companies that have a stabilized by 500' or 1000' policy, the rapid wind shift and resulting decrease below ref speed could result in sudden destabilization, requiring a go around from low altitude and low airspeed- which can be just as dangerous in some aircraft as attempting the approach in the first place.
03-01-2007 | 05:24 AM
#12
Libertarian Resistance
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From: 757 FO
03-01-2007 | 05:28 AM
#13
done, gone skiing
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From: Rocking chair
............So... how do you folks feel about a 30+ knot tailwind that changes to a 30+ knot direct crosswind as you descend down to 300 feet, and then slowly changes to 12 knots all the way down to touchdown?
How "safe" is it to fly an approach under these type of conditions?
How "safe" is it to fly an approach under these type of conditions?
How difficult is it to fly an approach under these type of wind conditions?
Landing with a 12kt x-wind is not the problem, adjusting from a 30kt tailwind is a problem. Ground speeds are high, and to maintain the proper decent angle on the final approach segment, you will need to have a higher than normal decent rate (relative to your "normal" profile) and a even more critically, a reduced power setting while flying with the tail wind. The transition to less tail wind will require more power, less decent rate and some pitch adjustment (all for the changing conditions) and that's without taking into account the "new" x-wind that wasn't there until the end.
Several adjustments to flight path and speed, plus a late x-wind to adjust to; good chance of coming in high and hot, if unaware or behind on setting up for the final approach.
Hope this answers your following questions.
03-01-2007 | 05:29 AM
#14
Gets Weekends Off
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From: Bus Driver
I worked the midnight shift last night at MEM during the FDX inbound/outbound, and I have a few questions about tailwind and crosswind components.
Here's the scenario: MEM was landing to the north, using RWY 36L and 36R. The surface wind is 090/08, so we were also using RWY 09 instead of RWY 27. The very first aircraft that checks in on the Tower frequency states that there is a "... direct 30 knot crosswind component from 2,000 feet down to 300 feet, then 12 knots direct all the way down to touchdown." I issue the PIREP to the next couple of aircraft, and am informed that it's actually a tailwind all the way down to 300 feet.
Replys from pilots receiving this PIREP were: "Oh God...", "Oh Lord", "That sounds like fun", "Oh geez", "What?", and other words and phrases indicating that the approach and landing were going to be very interesting.
We had several aircraft elect to go-around and try again; some aircraft rolled all the way to the end and were not able to turn off where we would normally expect; the long rollers caused at least one go around; and the requirement to issue these wind conditions to each arrival was simply excruciating and time consuming.
So... how do you folks feel about a 30+ knot tailwind that changes to a 30+ knot direct crosswind as you descend down to 300 feet, and then slowly changes to 12 knots all the way down to touchdown?
How "safe" is it to fly an approach under these type of conditions?
How difficult is it to fly an approach under these type of wind conditions?
Is this something that is fun and offers you an opportunity to display your skill, or is it something that you'd rather not be bothered with?
What is your company policy on these type of conditions?
What else should ATC know about your crosswind/tailwind concerns?
Does some guy in a suit at FDX mandate that you WILL land north under these conditions in order to save the company money?
Thanks,
MEM_ATC
Here's the scenario: MEM was landing to the north, using RWY 36L and 36R. The surface wind is 090/08, so we were also using RWY 09 instead of RWY 27. The very first aircraft that checks in on the Tower frequency states that there is a "... direct 30 knot crosswind component from 2,000 feet down to 300 feet, then 12 knots direct all the way down to touchdown." I issue the PIREP to the next couple of aircraft, and am informed that it's actually a tailwind all the way down to 300 feet.
Replys from pilots receiving this PIREP were: "Oh God...", "Oh Lord", "That sounds like fun", "Oh geez", "What?", and other words and phrases indicating that the approach and landing were going to be very interesting.
We had several aircraft elect to go-around and try again; some aircraft rolled all the way to the end and were not able to turn off where we would normally expect; the long rollers caused at least one go around; and the requirement to issue these wind conditions to each arrival was simply excruciating and time consuming.
So... how do you folks feel about a 30+ knot tailwind that changes to a 30+ knot direct crosswind as you descend down to 300 feet, and then slowly changes to 12 knots all the way down to touchdown?
How "safe" is it to fly an approach under these type of conditions?
How difficult is it to fly an approach under these type of wind conditions?
Is this something that is fun and offers you an opportunity to display your skill, or is it something that you'd rather not be bothered with?
What is your company policy on these type of conditions?
What else should ATC know about your crosswind/tailwind concerns?
Does some guy in a suit at FDX mandate that you WILL land north under these conditions in order to save the company money?
Thanks,
MEM_ATC
The very first aircraft gave you a bad pirep. There indeed was 30 kts of wind but in no way was it a 30 kt tailwind. We were vectored in to 36R that night. We showed winds at about 110-120 at 28-33kts @ 3000ft. NOT A 30KT TAILWIND. I'm sure the tailwind component on that works out to about 8-10kts. It pretty much settled down all the way to touchdown and was a direct crosswind at 15kts when we got over the numbers. No biggie!
03-01-2007 | 05:44 AM
#15
Gets Weekends Off
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From: B777 Captain
Other way around...
Lose a headwind and you're going to be pushing the power up to regain that airspeed. Lose a tailwind and your airspeed is going to jump up, requiring you to power back. Rapidly diminishing tailwinds can result in low power settings, high airspeed and high groundspeed. That in my book equates to long and fast landings.
Lose a headwind and you're going to be pushing the power up to regain that airspeed. Lose a tailwind and your airspeed is going to jump up, requiring you to power back. Rapidly diminishing tailwinds can result in low power settings, high airspeed and high groundspeed. That in my book equates to long and fast landings.
Landing South in this scenario would be a lot worse. Sounds like it is all within limits and safe. More than likely, those that landed long were carrying extra IAS intentionally, concerned about the PIREP issue. This whole scenario is just part of being a professional pilot.
03-01-2007 | 06:23 AM
#16
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Some pilots tend to believe in their wind readouts a bit too much.
I heard a captain once when I was on short final: "Wind 090 at 8 knots, now it's 10 knots, know it's 7, o.k. now it's 100 degrees at 10 knots...." This in a 30 year old DC-10 with 3 boat anchors for INS's.
The computer has to take your true velocity vector (derived from FMS/GPS/INS) and compare it against your true airspeed vector (derived from Pitot/Static/ADC/AOA/Sideslip data).
Errors are induced by landing configuration, turbulence, older equipment, slack autothrottles, and a host of other sources.
Bottom line - wind vector on final is a conversation piece only. That's why we use ground observation for limitation compliance.
I heard a captain once when I was on short final: "Wind 090 at 8 knots, now it's 10 knots, know it's 7, o.k. now it's 100 degrees at 10 knots...." This in a 30 year old DC-10 with 3 boat anchors for INS's.
The computer has to take your true velocity vector (derived from FMS/GPS/INS) and compare it against your true airspeed vector (derived from Pitot/Static/ADC/AOA/Sideslip data).
Errors are induced by landing configuration, turbulence, older equipment, slack autothrottles, and a host of other sources.
Bottom line - wind vector on final is a conversation piece only. That's why we use ground observation for limitation compliance.
03-01-2007 | 06:23 AM
#17
Thread Starter
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From: Austin Tower
FedExBusBoy,
The wind was constantly shifting throughout the entire inbound push. After landing, several pilots reported that the wind was exactly as reported to them on initial contact. Other pilots reported that it was more of a tailwind all the way down to 300 feet. Interesting conditions either way!
MEM_ATC
The wind was constantly shifting throughout the entire inbound push. After landing, several pilots reported that the wind was exactly as reported to them on initial contact. Other pilots reported that it was more of a tailwind all the way down to 300 feet. Interesting conditions either way!
MEM_ATC
The very first aircraft gave you a bad pirep. There indeed was 30 kts of wind but in no way was it a 30 kt tailwind. We were vectored in to 36R that night. We showed winds at about 110-120 at 28-33kts @ 3000ft. NOT A 30KT TAILWIND. I'm sure the tailwind component on that works out to about 8-10kts. It pretty much settled down all the way to touchdown and was a direct crosswind at 15kts when we got over the numbers. No biggie!
03-01-2007 | 06:31 AM
#18
Indian Takeout Driver
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From: FAR part 347 (91+121+135)
I think FedExBusBoy probably got it.. there is unlikely the same winds at 3000 as there is at FE.
As for the reason the tailwind is bad on landing... it has little to do with the possibility of a windsheer (assuming it's stead), and more to do (for me at least) with ground speed. The MD-11 as it is can have Vrefs well above 160, add 30kts to that with your landing roll and you're a test pilot.
As for the reason the tailwind is bad on landing... it has little to do with the possibility of a windsheer (assuming it's stead), and more to do (for me at least) with ground speed. The MD-11 as it is can have Vrefs well above 160, add 30kts to that with your landing roll and you're a test pilot.
03-01-2007 | 06:37 AM
#19
Thread Starter
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From: Austin Tower
FBH,
As mere Controllers, we are only able to provide the Supervisor with the PIREP of the wind conditions on the Final Approach Course. These folks are generally in the Tower/TRACON monitoring the operation, and they are aware of what the wind is doing. *** I *** am unable to "turn the boat around" and go the other direction. *** THAT *** is absolutely a decision that the Supervisor will make, and one that the Controllers will have to live with for the duration of the inbound push.
Some Supervisors are very good at adjusting to the changing wind conditions, and are more likely to go "into the wind", regardless of what an airline company might want to do. Other Supervisors are notorious for making a bad decision and sticking with it for the duration of the entire push.
There is some coordination between FDX and the FAA prior to each inbound and outbound operation. I'm not sure who it is exactly at FDX that calls to make this inquiry, but they always want to know what configuration we'll be using (north or south), and how many runways (1, 2 or 3). I would imagine this would help them plan for the sort, how much fuel for the outbound, and general timekeeping for doing business.
I find it interesting to note that we often find ourselves landing/departing under various wind conditions that would lead me to belive that a *** financial *** decision has been made over a safety decision. Then again, I'm not a pilot, and I don't understand the full capabilities of your aircraft... thus the questions regarding tailwind and crosswind approach/landings.
If it's okay with you guys, then it's okay with me.
MEM_ATC
My question to you is why haven't you changed flows upon recipt of the pilot report? Does "some guy in a suit" in the TRACON/TOWER decide you're gonna run operations with a 12kt tail wind? I don't understand the pilot/controller mind set that you are relaying in this post.
Some Supervisors are very good at adjusting to the changing wind conditions, and are more likely to go "into the wind", regardless of what an airline company might want to do. Other Supervisors are notorious for making a bad decision and sticking with it for the duration of the entire push.
There is some coordination between FDX and the FAA prior to each inbound and outbound operation. I'm not sure who it is exactly at FDX that calls to make this inquiry, but they always want to know what configuration we'll be using (north or south), and how many runways (1, 2 or 3). I would imagine this would help them plan for the sort, how much fuel for the outbound, and general timekeeping for doing business.
I find it interesting to note that we often find ourselves landing/departing under various wind conditions that would lead me to belive that a *** financial *** decision has been made over a safety decision. Then again, I'm not a pilot, and I don't understand the full capabilities of your aircraft... thus the questions regarding tailwind and crosswind approach/landings.
If it's okay with you guys, then it's okay with me.
MEM_ATC
03-01-2007 | 06:42 AM
#20
Line Holder
Joined: Sep 2006
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I worked the midnight shift last night at MEM during the FDX inbound/outbound
Replys from pilots receiving this PIREP were: "Oh God...", "Oh Lord", "That sounds like fun", "Oh geez", "What?", and other words and phrases indicating that the approach and landing were going to be very interesting.
Replys from pilots receiving this PIREP were: "Oh God...", "Oh Lord", "That sounds like fun", "Oh geez", "What?", and other words and phrases indicating that the approach and landing were going to be very interesting.
Even if said with levity, those remarks would be less than professional on the radio. (the "Oh God.., "oh Lord", "Oh Geez")
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