747-8: Flight Report

While trying to get a faster GS yesterday, I pushed up the speed a bit. Or at least I tried to. The plan was .90 (RVSM limit). In the 400, you select your speed, the autothrottles go up and obtain that speed. In the -8, apparently it won't let you fly in the yellow arc. You can see the selected speed, Mach .86 as shown by the magenta speed marker. But the airspeed wouldn't go into the yellow. The autothrottles increased thrust until reaching the top of the yellow, then reduced power to stay there. Of course, you can disconnect the autothrottles and push the power up yourself.

It's interesting to note the large yellow arc at the top end of the airspeed. The 400 doesn't really have one. At a few altitudes there's a small one, but only a few knots. I've been told that the -8s wing ended up stiffer than planned, which created a few problems. Using software and fly by wire, the spoilers and ailerons can both deploy upwards to reduce wing load. Anyways, the top limit is a result of the stiffer wing.

So 701 GS was the best we saw on this flight. On the 400 we could have easily gotten another 20 knots.
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Yeah, the 747 classic would go right to barber pole (.92) easily. The 400 starts to mach buffet right around mach .90. It's noticable. I've only had the -8 to mach .88. Maybe next week I'll see where it's buffet is.

The yellow arc is defined by altitude. Probably temperature too as it's related to mach. It doesn't show up until the mid 20s if I remember right. Maybe high 20's.

As far as pulling breakers, these newer planes report everything back to the company. If a breakers out, they'll know it.

The -8 is definitely strange as far as altitudes go. In the 400, if you're a little heavy for an altitude, you can just fly faster and the margins are better. Say you're flying at mach .84 at 33000 and you're heavy. Max altitude may be 33200. But if you speed up, max altitude goes up. Say you fly .86, then max altitude may be 33400. But the -8 is the opposite. Speeding up makes thing worse and max altitude goes down. It must be because to that top yellow arc that really isn't present on the 400.

I'll try and get more info. It's nothing we really have to deal with, and not of any real significance. We just fly the altitudes the FMS calculates within reason.

 

As far as a part 25 aircraft and a yellow arc, I'm not sure. It's definitely not like the yellow arc in light aircraft. Again, I'll see what info I can pull up.

 

No, not me. They won't let me fly to Europe. Actually, I just try and stay across the Pacific to keep my trips shorter.

NCA is up to 5 747-8s now. All the west coast to Japan flying is on the -8. When I fly the occasional 400, it feels a bit strange.

It's the season for windshear in Narita. SW winds, even when relatively light, can make for an interesting approach. I saw this Lufthansa A340 in the NCA hanger yesterday in Narita. Apparently this landing ending up being 2.8 G's. Not sure how much damage.

https://www.youtube.com/watch?v=UK5Nm_rKu50

Not sure how to embem that video to play directly from FChat.....

 

Thanks so much. The switches just aft and outside of throttles #1 and #4 are the autothrottle disconnect switches. You disconnect them using your thumb. So the captain would typically use the one by the #1 throttle and the FO the one by the #4 throttle. Pushing once disconnects the autothrottles, but a warning appears on the EICAS and a beeper sounds announcing the disconnect. Pushing twice disconnects and keeps the warning inhibited. So we typically push that button twice.

There are also 2 switches almost identical to those in front of throttles #2 and #3. They are the Go Around switches. You can't see them in this picture. Anyways, there have been quite a few cases of pilots accidentally pushing the Go Around switches instead of the autothrottle switches.

I borrowed this pic off the web. I'm flying back LAX SFO NRT tonight and will try and remember to take a pic showing those switches.
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All the 747 classics (including the SP) : 375 kts or .92
The 400 : 365 kts or .92
The -8 : 365 kts or .90

The classic could be flown at .92 without a problem
The 400 starts to mach buffet and shake at .90
The -8, not sure. I've only been at .88 No buffet

I've heard the 727 is a great "pilots" airplane. I would have liked to have flown it.

 

Here's a pic of the throttle quadrant showing the Go Around switches above throttles #2 and #3. This is a -8, but it's the same on the 400 too.
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