What it's like to fly an airliner.

Astro14

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Hey BITOG, the United threads keep getting shut down, but in those threads, questions have come up about what's it like to fly an airliner, or how airplanes work. As many of you know, I'm a pilot for United. Over the past 20 years with United, I've flown the 747, 757/767 and A-320. I was an instructor on the 747-400 and the 757/767

So, I would like to start a thread focused on the airplanes. Much like I did a few years ago with the F-14, here:

Please avoid the contentious aspects of airlines that have resulted in the closing of previous threads. Stick to the airplane questions, and I'll be happy to answer.

Here's a start from this morning:

Originally Posted By: PimTac
Mentioning the 757 reminded me of a flight I was on a few years ago out of Hong Kong. This was not United but Cathay Pacific. The aircraft took off and climbed at a pretty good angle. Having flown out of there a number of times this was new to me. That 757 was like a rocket. At around 3000 feet ( not sure exactly) the captain pulled back on the throttles and we experienced the sensation of stopping in mid air. It was very noticeable and then it started to feel like the plane was falling backwards. A few passengers screamed. One young girl a couple of rows ahead of us was crying.

That sudden change in forward motion was a very weird sensation. I wonder if that maneuver was as planned or unexpected for the flight deck crew as well?


OK - I'm pretty certain that I know what happened, but the explanation is technical, so bear with me...

Depending on weight, wind, runway length, terrain, weather, noise-abatement requirements, etc. we may use full power for takeoff. If we do, in a 757, it's pretty sporty. The airplane has great thrust/weight for an airliner.

We used to do this all the time in Orange County, CA, and in fact, because it was dramatic, we were required to brief the passengers that the takeoff would be steep, followed by a substantial power reduction at level-off. And that always was dramatic. A 20 - 22 degree nose up climb followed by a nose-over level-off and big power reduction.

Hong Kong, whether the old Kai-Tek, or the new Chep Lap Kok, doesn't really have noise abatement concerns, so I don't think it was that in your experience.

The Flight Management System (FMS) on the 757/767 drives the flight director and/or autopilot as well as the autothrottles. In a full power take off with a low level level-off, the system can get pretty aggressive. There are a couple of modes that manage pitch and power, one is VNAV, one is Flight Level Change, we'll skip the other.

VNAV (Vertical Navigation) manages pitch and power to comply with vertical crossing restrictions, published speed restrictions and fuel vs. time climb speeds. Pretty sophisticated interface between navigation and managing fuel. Flight Level Change is simple: full power (or idle if descending) to get to the altitude desired using a manually selected speed.

What can happen is this: as the FMS responds to the rate of climb, which is high in a full-power takeoff, it "captures" the altitude early...it's judging how quickly it can lower the nose from a steep climb, either via Flight Director guidance or using the autopilot. In a low-altitude level off, the FMS is still using V2+15 knots as its reference speed (so, a much slower speed than climb speed, call it 170 knots, or something similar on a 757), so, when it captures the altitude (meaning that elevator pitch commands will now be to maintain the altitude instead of a climb speed) in VNAV, the airplane FMS commands the autothrottles to maintain that speed.

As the airplane is leveling off, and the throttles are coming back, because it was at full power, and because it was climbing so rapidly, and because the throttles are coming back smoothly, the airplane frequently gets well ABOVE V2+15, so those throttles just keep coming smoothly back to idle to get the airplane to the commanded V2+15 speed. You get a pretty big change in pitch and power.

There's a somatogravic illusion that the airplane is falling, or decelerating...it is decelerating, but just a bit. Your inner ear is lying to you: it went from accelerated motion (takeoff, and then the climb) to steady motion, but the change feels to you like you're decelerating and now descending...you're not, but it feels that way.

Up front, it feels rough - a too-agressive correction to maintain altitude and a glitch in wanting to maintain an inappropriate speed. When the airplane levels off, we want it to keep accelerating through the flap retraction speeds, but if VNAV captures at low altitude, it wants to stay at V2+15.

So...

Experienced 757 drivers use FLCH when leveling at low altitude to prevent the glitch above. When FLCH captures the altitude, we simply dial up a manual speed selection and the power remains steady as the airplane levels off and begins to accelerate.

Pilots that come from other airplanes are used to the more sophisticated VNAV, and they tend to prefer the more automatic mode as "better" but in this case, VNAV just isn't a good choice.

In fact, our flight manual cautions that "Flight Level Change should be used for level-offs of 3,000 feet and below" - which is nearly every day in EWR...

So, full power takeoff, and a crew that elected to use VNAV - and you got a fairly uncomfortable level - off.

It's a 757 thing...

Cheers,
Astro
 
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thumbsup2.gif


I enjoy your posts, thanks for typing that out.
 
I had a similar mild panic attack when flying out of Phoenix about 15 years ago. We took off normally but once we hit a certain (still low) altitude, nose still a little high, the engines throttled back and it felt like we were falling out of the sky. It set off the "this can't be right" alarm bells in my head and looked around in a panic to see if anyone else was startled. The guy next to me noticed and said I could relax, it's just because of the residential area at the end of the airport property. Pilots weren't allowed to climb with the engines screaming until they were beyond a certain point. The just had to get airborne, idle for a few minutes, then power up and climb. It was extremely unnerving.
 
Thanks Astro. We bug smashers love hearing about the big birds. Love the 757. Will look forward to your posts.
 
Originally Posted By: Bottom_Feeder
Pilots weren't allowed to climb with the engines screaming until they were beyond a certain point. The just had to get airborne, idle for a few minutes, then power up and climb. It was extremely unnerving.


I had that happen at John Wayne as Astro describes for noise abatement. Like you, it scared the dickens out of me the first time. The angle was such that you'd think a compressor stall would happen.

One other more dangerous time was coming out of Newark. The power came back abruptly and we went light in our seats for a few seconds. The pilot later told us that he had been cleared up into the path of another plane going in the same direction of travel. When ATC noticed their error they issued a very short, sharp command to stop climb and descend. Bit of a heart pounder.
 
Originally Posted By: Astro14
...we may use full power for takeoff. If we do, in a 757, it's pretty sporty.


That is my new favorite industry term / euphemism / understatement. "Pretty sporty".
crackmeup2.gif
 
Originally Posted By: Ethan1
Originally Posted By: Astro14
...we may use full power for takeoff. If we do, in a 757, it's pretty sporty.


That is my new favorite industry term / euphemism / understatement. "Pretty sporty".
crackmeup2.gif



Well...if I said it was "fun"...people might take offense...

And we really did have a prepared announcement in our pubs for John Wayne airport - it went so far as to tell us when to read it!

I always tweaked it a little...I thought it was a bit...dry...

I should point out that we trained that take-off in the simulator, including an engine failure just after reaching the target pitch attitude...to keep the airplane under control, we had to lower the nose rapidly, before the speed started to decay and cause control problems...

That, too, was...sporty...

Cheers,
Astro
 
Originally Posted By: Bottom_Feeder
Pilots weren't allowed to climb with the engines screaming until they were beyond a certain point. The just had to get airborne, idle for a few minutes, then power up and climb. It was extremely unnerving.


I had that happen at John Wayne as Astro describes for noise abatement. Like you, it scared the dickens out of me the first time. The angle was such that you'd think a compressor stall would happen.

One other more dangerous time was coming out of Newark. The power came back abruptly and we went light in our seats for a few seconds. The pilot later told us that he had been cleared up into the path of another plane going in the same direction of travel. When ATC noticed their error they issued a very short, sharp command to stop climb and descend. Bit of a heart pounder.

That...or the TCAS went off and the crew responded to the RA (resolution advisory)...which can command pitch changes right at the max rate of the airplane to avoid a mid-air collision.

NYC Metro area is pretty dynamic...a lot of airplanes, including VFR, and some very crowded airspace...
 
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The first time I flew on an airliner (737) I was a nervous wreck! Our steward (super cool guy!) saw how nervous I was and brought me a few Jack and Cokes. Next thing I remember I was waking up as we were landing haha. He didn't even charge us for the drinks
laugh.gif
 
My youngest son just got out of actvive duty with the USAF. He flew, and was an instructoir pilot, on the C-17. He just got a job with Delta and currently flies the A320. I have no clue where his passion for flying came from. I absolutely do not like flying. Nice thread Astro.
 
Appreciate the insight and the effort to bring quality threads to bitog..

something sorely needed.. you can only have so many "what oil in my XXXXXX" threads.
 
Originally Posted By: Astro
That...or the TCAS went off and the crew responded to the RA (resolution advisory)...which can command pitch changes right at the max rate of the airplane to avoid a mid-air collision.


I noticed recently while working on the leases mentioned elsewhere that both TCAS and TCAS II are expensive adds to an aircraft. But TCAS II, with RA, was about $150K more and helped drive the lease price up! What causes that?
 
This has the makings of a great thread. Thanks Astro for starting it.

Way back in the mid- seventies, I was a passenger on a Wien Air Alaska flight out of Kodiak headed for Anchorage AK. It was a snowy morning in December and the snow was building on the roads making it a bit slick. All was normal as the plane transited the runway back to the takeoff point. In those days the main island highway crossed the runway there so there were traffic lights to keep things clear. That end of the runway was also at the foot of Mt. Barometer, a tall hill of a few thousand feet. The runway pointed out towards the ocean. I'm sure pilots loved flying in and out of this place.

The takeoffs there are what I like to call carrier style. Gun the engines and then pop the brakes and off you go. This flight started that same way but as we really got going I could feel the plane turning slightly one way and then the other way. I'm sure I wasn't the only one who left deep impressions in the armrests. Soon after we lifted off and I could hear and feel a sigh of relief from everyone.

About a minute later, the Captain came on the intercom to announce that the Kodiak airport was now closed.

I would imagine a humorous statement like that wouldn't go over too well today but on that morning the passengers were chuckling.
 
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I'm not sure if it was mentioned in some other thread, but I just watched Sully and it didn't really go into how tricky it is to land a plane without power in the water. I think Sully had flown gliders before but of course nothing that size. Have you ever tried that in a simulator?
 
Originally Posted By: Astro14
Hey BITOG, the United threads keep getting shut down, but in those threads, questions have come up about what's it like to fly an airliner, or how airplanes work. As many of you know, I'm a pilot for United. Over the past 20 years with United, I've flown the 747, 757/767 and A-320. I was an instructor on the 747-400 and the 757/767

So, I would like to start a thread focused on the airplanes. Much like I did a few years ago with the F-14, here: https://bobistheoilguy.com/forums/ubbthreads.php/topics/3884297/1

Please avoid the contentious aspects of airlines that have resulted in the closing of previous threads. Stick to the airplane questions, and I'll be happy to answer.

Here's a start from this morning:

Originally Posted By: PimTac
Mentioning the 757 reminded me of a flight I was on a few years ago out of Hong Kong. This was not United but Cathay Pacific. The aircraft took off and climbed at a pretty good angle. Having flown out of there a number of times this was new to me. That 757 was like a rocket. At around 3000 feet ( not sure exactly) the captain pulled back on the throttles and we experienced the sensation of stopping in mid air. It was very noticeable and then it started to feel like the plane was falling backwards. A few passengers screamed. One young girl a couple of rows ahead of us was crying.

That sudden change in forward motion was a very weird sensation. I wonder if that maneuver was as planned or unexpected for the flight deck crew as well?


OK - I'm pretty certain that I know what happened, but the explanation is technical, so bear with me...

Depending on weight, wind, runway length, terrain, weather, noise-abatement requirements, etc. we may use full power for takeoff. If we do, in a 757, it's pretty sporty. The airplane has great thrust/weight for an airliner.

We used to do this all the time in Orange County, CA, and in fact, because it was dramatic, we were required to brief the passengers that the takeoff would be steep, followed by a substantial power reduction at level-off. And that always was dramatic. A 20 - 22 degree nose up climb followed by a nose-over level-off and big power reduction.

Hong Kong, whether the old Kai-Tek, or the new Chep Lap Kok, doesn't really have noise abatement concerns, so I don't think it was that in your experience.

The Flight Management System (FMS) on the 757/767 drives the flight director and/or autopilot as well as the autothrottles. In a full power take off with a low level level-off, the system can get pretty agressive. There are a couple of modes that manage pitch and power, one is VNAV, one is Flight Level Change, we'll skip the other.

VNAV (Vertical Navigation) manages pitch and power to comply with vertical crossing restrictions, published speed restrictions and fuel vs. time climb speeds. Pretty sophisticated interface between navigation and managing fuel. Flight Level Change is simple: full power (or idle if descending) to get to the altitude desired using a manually selected speed.

What can happen is this: as the FMS responds to the rate of climb, which is high in a full-power takeoff, it "captures" the altitude early...it's judging how quickly it can lower the nose from a steep climb, either via Flight Director guidance or using the autopilot. In a low-altitude level off, the FMS is still using V2+15 knots as its reference speed (so, a much slower speed than climb speed, call it 170 knots, or something similar on a 757), so, when it captures the altitude (meaning that elevator pitch commands will now be to maintain the altitude instead of a climb speed) in VNAV, the airplane FMS commands the autothrottles to maintain that speed.

As the airplane is leveling off, and the throttles are coming back, because it was at full power, and because it was climbing so rapidly, and because the throttles are coming back smoothly, the airplane frequently gets well ABOVE V2+15, so those throttles just keep coming smoothly back to idle to get the airplane to the commanded V2+15 speed. You get a pretty big change in pitch and power.

There's a somatogravic illusion that the airplane is falling, or decelerating...it is decelerating, but just a bit. Your inner ear is lying to you: it went from accelerated motion (takeoff, and then the climb) to steady motion, but the change feels to you like you're decelerating and now descending...you're not, but it feels that way.

Up front, it feels rough - a too-agressive correction to maintain altitude and a glitch in wanting to maintain an inappropriate speed. When the airplane levels off, we want it to keep accelerating through the flap retraction speeds, but if VNAV captures at low altitude, it wants to stay at V2+15.

So...

Experienced 757 drivers use FLCH when leveling at low altitude to prevent the glitch above. When FLCH captures the altitude, we simply dial up a manual speed selection and the power remains steady as the airplane levels off and begins to accelerate.

Pilots that come from other airplanes are used to the more sophisticated VNAV, and they tend to prefer the more automatic mode as "better" but in this case, VNAV just isn't a good choice.

In fact, our flight manual cautions that "Flight Level Change should be used for level-offs of 3,000 feet and below" - which is nearly every day in EWR...

So, full power takeoff, and a crew that elected to use VNAV - and you got a fairly uncomfortable level - off.

It's a 757 thing...

Cheers,
Astro


Astro,

I had a low altitude VNAV capture in a 757 after takeoff in BWI one night, the low altitude capture combined with a required turn right after takeoff caused the power to come back to idle as we had to level off at 2000' prior to a right turn. That rapid reduction in power caused our new hire lead flight attendant to become alarmed that we lost all power and she promptly called up front in an urgent manner to tell us that something was wrong. (Big no-no for flight attendants to call us below 10,000' unless there is a fire in the cabin or some other life threatening condition.)

You're right about SNA. It get's everyone's attention when that power reduction comes - and we have to stay low to avoid the inbound traffic into LAX.

You're also right about using FLCH. I use it all the time when step climbing for short changes, i.e., 7,000 to 9,000'. Some guys will go to VNAV and of course the power will come up and the airplane will start climbing like crazy only to have the power come back abruptly at ALT CAP with a corresponding slower than desired speed. FLCH is your friend below 10,000' is the old saying, but it works well in many circumstances.

Fly safe,

757Guy
 
One of my favorite flying memories is from a airliner landing, first of all we seemed to drop a bit abruptly on close approach but then had a big delay from that to the initial touch down.
Then we hit the ground harder than usual, and, oops, we were back up again. Another hard hit and back up!
We finally hit the ground to stay, but the plane was rotated about its longitudinal axis just a bit and we seemed to be rolling on only one side of the landing gear...then, bam, the other set is now on the ground!
All of us passengers were looking at each other with puzzled, yet amused, looks on our faces...the intercom comes on and we hear something like, "This is Captain Jones wishing to congratulate First Officer Smith on his first ever landing of a 737-XXX!!!"
There were some boos, some sarcastic cheering, and lots of noise in general from the passengers.
Then poor Smith had to stand by the cockpit door and bid farewell to the passengers, many of whom offered rude comments...he looked sort of like wanted to melt away and sort of like he wanted to punch a few people out. I just smiled and tipped my cap to him.

Is it common for a crew member to be shamed like this if he has a bit of trouble?
 
What is the "sportiest" thing a commercial airliner- of any model is capable of?


Also, thank you for taking the time to put yourself out there and do a Q &a A!
!!
 
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