744 Real-Life

[Guest Concordeguy]

Does the "Queen" actually go 250 something knots at 37,000 feet or whatThanx, Christian Aponte

[mburkhard 23]

> Does the "Queen" actually go 250 something knots at 37,000>feet or whatIn "real life" the Queen does not go any knots but MACH at 37'000 feet. Around .84 - .86 Mach.Regards,Markus

[Guest Concordeguy]

pardon my error, ThnxChristian

[Guest D17S]

Also keep in mind this 250 kts you are looking at on the PFD

[Azapata87 173]

thanks Sam, very interesting read! Andrew

[jordanal 70]

Sam,"like some goofy, MSFS induced erraticism"Is that what you call that? I always wondered, LOL... Very good...BTW, Do they ever run 'em up above .86 Mach. My PMDG QoS flies well at .90 Mach (load dependant, of course) at 95%N1 at FL380. Just curious if real 747 captains are ever allowed to put the pedal to the metal if conditions warrent.Yup, you're correct! I don't exactly drive the speed limit on highways either, LOL...AL | KCHS - Charleston, AFB | Home of the 437AW (53 C-17's)-------------------------------------------------------------Game Rig:AMD64-4000+ SanDiego OC=220/440/2640 | Asus A8N-SLI Deluxe | Corsair TwinX2048-3200C2PT (2x1GB) 2.5-3-3-8/1T@2.8v | Evga NV 7900GT v84.56 (No OC yet)| NV LAN@1GB | NV SATA-I Raid-0 223GB (3x80GB Samsung) (WinXP/Games) | NV SATA-II WD 320GB (Backups) | IDE-0 80GB Samsung (Archive) | Realtek AC'97 5.1 Surround | CH Yoke, TQ, & Pedals | FS9.1 | WideFS Server | FSUIPC v3.6 | FSGenesis Mesh (All) | PMDG (All) | PAI (All) | FSBuild2 | Etc...FS9 Support Rig:AMD3200+ | Gigabyte GA-7NNXP | Leadtek NV 5900 | Corsair TwinX1024-3200 (2x512MB) | Intel LAN@1GB | SiI3112 SATA-I 80GB Samsung | IDE-0 80GB IBM | JustCom 4port KVM | FS Wide Client | ActiveSky v6 | Radar Contact v4 | FS Real Time | FS Flight Keeper | FS Commander | AI Smooth

[Guest D17S]

"BTW, Do they ever run 'em up above .86 Mach. My PMDG QoS flies well at .90 Mach (load dependant, of course) at 95%N1 at FL380. Just curious if real 747 captains are ever allowed to put the pedal to the metal if conditions warrant."There's an interesting question. The cost index number will set your FMC calculated Econ airspeed. Of course they don't just fill 'er up and blast off (like I tend to do). I imagine that the flight planners will work through the numbers and decide on a balance between speed vs fuel burn. This is the process that determines the cost index number. But if the boss just decides he wants to wind it up during a flight, there needs to be a very thoughtful analysis to determine if there will be enough fuel on board to make the destination with all the required reserves, etc. Watch the tread on the UAL flight that is in progress right now. Notice the tight focus on the fuel numbers and how they are affected by winds, old vs new airframes, even reducing GWs that will normally occur during a climb. There's some great detail there. This flight planning is going to be yet another 'brave new world' for us to explore (i.e., the real one). Also, as the FMC sees the Econ speed increasing, it will (should?) decrease the Vnav cruise page's Max altitude number. For instance at say M.82, the airplane will be able to maintain airspeed at a higher altitude than it will at a faster M.86. Who's got a flight going. Try a higher cost number. When the ECON airspeed increased, did the MAX altitude decrease? How can you tell when you are at your absolute, MAX altitude for any given airspeed? First pick your test airspeed and stabilize there. Watch actual cruise thrust vs the CRZ, EICAS thrust limit. Thrust should always be a bit below an EICAS, CRZ thrust limit when you are in a VNAV PATH/SPD stable cruise. If thrust is still below that CRZ EICAS thrust limit, climb a bit. Use climb thrust to climb, but when you are back level and in stable cruise, re-select CRZ as your EICAS thrust limit. Once your actual thrust level touches that CRZ thrust limit in cruise, you're done. Don't go an inch higher . . . . . and watch out. Now you have to be extra careful that you don't run into any of those pesky erraticisms! They will send you tumbling head over heals. Yeaa haaa. Stall city, here we come. So is 95% N1 right at EICAS CRZ thrust limit? If you still have a little room, all's well. Although .90 mach has gotta be getting close to some kind of Vne (never exceed).

[Guest capntom]

Albuqurque Center once asked us on out way to SFO if we could give them best possible fwd speed.... "Nine Oh OK?" She does just fine at M.90, shakes a little and ya can see shockwave standing up about 10 ft inside the winglets, but she goes really well!M.90 is currently an airspeed limitation for us in RVSM airspace.Tom

[jordanal 70]

Hmmm, haven't seen any shockwaves yet, even at .91M on my PMDG QoS, LOL. Now I'm gonna have to go even faster to see if they show up. Guess the passengers on my next trip should probably just stay buckled up for the entire cruise-phase. I wonder if they can hear the overspeed warning from the back, LOL... On second thought, I'll head over to the FSX forum for a feature-request, LOL...That is actually a good feature-question for the FSX forum, wondering if the new ATC will regulate/designate speed other than the 250Kt/10K.AL | KCHS - Charleston, AFB | Home of the 437AW (53 C-17's)-------------------------------------------------------------Game Rig:AMD64-4000+ SanDiego OC=220/440/2640 | Asus A8N-SLI Deluxe | Corsair TwinX2048-3200C2PT (2x1GB) 2.5-3-3-8/1T@2.8v | Evga NV 7900GT v84.56 (No OC yet)| NV LAN@1GB | NV SATA-I Raid-0 223GB (3x80GB Samsung) (WinXP/Games) | NV SATA-II WD 320GB (Backups) | IDE-0 80GB Samsung (Archive) | Realtek AC'97 5.1 Surround | CH Yoke, TQ, & Pedals | FS9.1 | WideFS Server | FSUIPC v3.6 | FSGenesis Mesh (All) | PMDG (All) | PAI (All) | FSBuild2 | Etc...FS9 Support Rig:AMD3200+ | Gigabyte GA-7NNXP | Leadtek NV 5900 | Corsair TwinX1024-3200 (2x512MB) | Intel LAN@1GB | SiI3112 SATA-I 80GB Samsung | IDE-0 80GB IBM | JustCom 4port KVM | FS Wide Client | ActiveSky v6 | Radar Contact v4 | FS Real Time | FS Flight Keeper | FS Commander | AI Smooth

[Guest gremel]

I think the aviation term for this kind of flying is called nearing the "coffin corner". The infamous "Coffin corner is a dangerous portion of the flight envelope that must be carefully approached by high altitude high subsonic speed aircraft, such as the Lockheed U-2 aircraft."Regards,jack

[Tabs 2,790]

Methinks an Ops article on indicated airspeed might be in order... ;)

[downscc 1,327]

Besides "coffin corner," the early swept wings suffered from "jet tuck" which is an uncontrolled pitch down cause by the center of lift moving too far aft at transonic... I remember the stories but I think they were all military. I don't think Boeing has ever had this problem. Once jet tuck started there weren't very many options.

[Guest D17S]

The old DC8s (-71s, 73s) I mess with have a pitch trim actuator to deal with this mach tuck aero-dynamic. It's a small electrical actuator that is literally attached to the FO's control column. There's a 1950s looking electronics box under that captains brain bag tray . . . with its very own pitot and static lines attached. What a crusty spot that is! At mach .something, the amp (that's what they used to call computers) starts to drive the actuator. That pitch trim actuator physically pulls the control column(s) back. There's an indicator rod that starts to poke out of a tube that is attached to the FO's control column. That's the Pitch trim's "annunciation." This is a completely independent system that is entirely separate from the AP.Quite the 1950s (60s airplane, but 50s design era) deal. Changing that actuator's a major PITA. Your right though, as far as I know. I haven't seen anything like it on any Boeings. How about a little DC8 trivia? After all, the topic heading is Real Life. Here ya go. That ol' DC8 is still quite the trooper. They're up to 80,000 to 100,000 hour airframes. But even at that, their dispatch reliability has always been (and still is) 3 points better than its equally unloved, yet younger counterpart, the 747-1/200 fleet. To the uninitiated, that's a big deal . . . a very big deal. The DC8 is fast, long range and can carry a load. But finally they were taken out of international service. The HFs (High frequency radios) were just giving operations (the pilots) fits. The engineering department kept issuing work orders for mechanics to check out main, RF coax cables with DC ohm meters. Checks OK? Well, no kidding! (Non-Radio guys believe me. This is like troubleshooting a race car's slow lap times by making sure all 4 tires are attached . . . them giving up! Then presenting a final conclusion to the owner: "It's haunted. Buy another race car.")They never did spring for an FDR . . . or any kind of RF test equipment. Guess they figured a mechanic should be able to whoop-up some sort of psychic connection or that employee just wasn't worth their salt (and should seek other employment?). So, sorry about the real world expo, but here it is: . . . Feeling the squeeze, HF write-ups received one "Checks OK" after another, then launched. And of course, they never got fixed. Mx managers were getting 'em over their respective fences and management Chief Pilots defended: "Hey, my boys still have their VHF radios. Let 'em call the guy behind them. Their HFs are probably working and they'll relay." As long last, even the most

[Guest capntom]

Actually the 747 does not hve any "Mach Tuck" type problems and has been flown to the limits of the transonic regiem in flight test (something on the order of M0.998) , and supesonic by some (ahem) gentlemen who had some other aircraft control issues. Coffin corner occurs when you get into the area of the flight envelope where the transonic limit for the aircraft and the stall speed converge. In some aircraft, particularly those with unstable transonic charcteristics such as mach tuck, high altitude upset could be quite hazardous. Early Lears were noted for this.Flying the Whale at Nine Oh is not in the least hazardous, but does up the fuel consumption (your mileage may vary).Tom

[cowpatz 243]

Christian to answer your original question.....yes it does do 250 kts at 37000ft. In fact considerably faster than that too.On a RW flight from LAX to AKL I noted the figures as follows (GE powered):FL380CI= 50IAS=270TAS=492Mach No=.846SAT -55We are now flying with a CI of 50 instead of 100 in the interests of fuel economy. Doesn't really do much in my opinion. You save about 300 kg but lose about 11 min on a typical 12 hr flight. Personally I think the initial ECON speeds are too low (at heavy weights) and as a consequence the body angle is too high which significantly inceases form drag. It always seems to perform better at faster speeds (than ECON) at the higher weights.I have seen the odd occasions where guys have been climbing in a mode other than VNAV and have left the speed window open with IAS set instead of MACH. You sure feel stupid when the unforecast clear air turbulence you are experiencing is actually mach buffet!!!!! :)CheersSteve