TWA884

The TWA 767s routinely cruised at 40-41K feet when I was flying them to and from Europe in the late 80's and the 90's.

huey_driver

Ok, I have resisted asking this, but apparently I am not the only one who does this... (good to know!)
I realize, its just a phone, but its fairly accurate on the ground. And I know (at least it used to be true) in Class A, everyone goes off pressure altitude. And I realize altimeters are linear but the change in pressure with altitude is not exactly linear.
Anyone want to take a stab at why I routinely see a difference of up to 2000 ft between the ISE flight tracking and my phone?
Its always to the high side, ie, GPS MSL (from my phone) is higher than flight tracking.
Maybe its just too long to explain, so thats a perfectly legitimate answer, or it may have been asked before but I didnt see it in this thread.
Is there really that much difference between True and Pressure altitude at FL400?

Edit: I guess answering my own question, there is that much difference. I couldnt figure figure out which way the difference went but realize now that pressure alt is always lower than true alt at those levels.... Finally found a table that I could understand....

tryathlete

As a pilot, I realize the FAA allows for “special” landings on parallel runways like SFO. Yesterday landing at SNA, we landed as we were passing a Cessna 172 on what appeared to be a taxiway to the left of our aircraft. Our pilot landed pretty hard perhaps unrelated but it was kind of freaky to see an aircraft so close to our left side.

When I learned to fly at CMI (Willard Airport) we landed on taxiways adjacent to commercial operations but we NEVER landed at the same time as commercial aircraft.

LarryJ

The GA airplane was landing on the shorter runway 20L (2,886'x75'). It is used as a taxiway during the morning airline push, when the overnight noise curfew ends, but it's a runway. The 20L traffic is VFR and is not separated (by ATC) from the traffic landing 20R. Traffic point-outs are exchanged and the pilot keep themselves separated visually.

The hard landing was due to runway 20R being 5,700' (x150') long. That is very short for an airliner. The goal is to touchdown by the 1,000' fixed-distance markers to ensure plenty of room for stopping. You'll also notice that the autobrakes are almost always set to MAX on those landings which produces a rather abrupt application of braking just after touchdown. You'll likely then feel the autobrakes disengage, which is very difficult to do smoothly in the 737, as soon as adequate stopping distance is assured. Not the smoothest arrival due to the short length of the runway.

IAH-OIL-TRASH

Is Harrison Ford playing pilot again??

LarryJ

Actually, the taxiway he landed on would have increased the distance from the Rwy 20R traffic.

tryathlete

Aha! I looked up the airport map and sure enough two runways. Now I get the hard landing and sure enough we felt the autobrake come off too!

threeoh

This is why I always brace my hand on the seat ahead of me before landing at MDW!

zeus2120

This might be an anecdotal observation, but is there any specific reason that landing / braking in a 737 sounds and feels vastly different than in a 787? I guess what I'm trying to say is most of the time 737 landings have vigorous overhead bin shaking and a pronounced feeling of braking -- but on my most recent 787 landing, it was virtually silent in the cabin. Just me or is there any reason for the difference?

LarryJ

I've ridden on 787s twice, but don't remember the details of the landings, and have never flown them so I don't know any specifics.

In the 737s we use autobrakes on almost every landing. They will apply the brakes when a set of conditions are met with the result of brakes being automatically applied shortly after main wheel touchdown. We also initial use full reverse thrust which is loud and causes some vibration. Later in the landing roll we apply manual brake pressure until the autobrakes disengage. On the 737, it is difficult to make this transition smoothly, particularly when there's a strong crosswind and you're still holding rudder pressure for directional control. The 787 is a much newer design so I would expect improvements in most, if not all, of these factors.

TomMM

Is reverse thrust coupled to the autobrakes?

LarryJ

No. We operate the reversers manually. On the 737, the procedure is to go initially to max reverse. At 80 kts airspeed we move toward reverse-idle so that we can stow the reversers by 60 kts.

The autobrakes have multiple settings. Each setting commands a set deceleration rate. When reverse thrust is used it causes some deceleration so the autobrakes provide less friction braking to maintain the same rate of deceleration.

On the 737 fleet, our procedure is to use autobrakes on every landing. I tend to go with the lowest setting that shows it will stop the airplane on the available runway because that makes it easier to manage the deceleration, and transfer to manual braking, more smoothly. On a short runway, like SNA, you'll almost always be on MAX autobrakes in the 737 which is pretty aggressive.

HkCaGu

When the actual atmosphere is WARMER than the standard atmosphere (15C/59F at sea level, decreasing with the standard lapse rate), each layer of pressure differences is thicker than the standard atmosphere, so the pressure decreases slower with height than the standard atmosphere...

TomMM

Where does the IFE system obtain the flights stats from? Flew FRA-ORD today on a 787 and shortly after touch down the flight information zeroed out. On some flights I've been able to watch the speed on rollout and taxi.

LarryJ

I don't know. That isn't discussed in our manuals. It must come from our flight management system but I don't know how.