flymatt2bermud
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RE: FL510 Pros Vs Cons?

Tue Feb 16, 2010 9:05 pm

Quoting cpd (Reply 49):
Back when Concorde was being designed, I'm pretty certain radiation was far from an exact science

I am not so certain that there are any real conclusions from the information scientists have gathered over the years.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
ElpinDAB
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RE: FL510 Pros Vs Cons?

Wed Feb 17, 2010 7:32 am

Quoting FlyMatt2Bermud (Reply 43):
Can anyone elaborate on more radiation specifics?

There is a great tool on APC to calculate the radiation that you received for a given flight: http://www.airlinepilotcentral.com/frame/radiation_profile.html

I personally can't relate microsieverts into common language though, unfortunately. Here is an APC thread on the topic: http://www.airlinepilotforums.com/ha...-fun-radiation-calculator-apc.html . I remember reading a good one about radiation exposure and pilots, either on APC or a.net, probably about 6 months ago, but I really don't know where I saw it, otherwise, I'd post a link. It was nice to read though. I'm not sure if it's the linked thread or not though...I apologize.

The dynamics of flying at FL400's+ have always fascinated me though. I'd love to see SST and even Suborbital concepts reborn, and this would definitely involve high radiation exposure for pilots. It's a risk that I would take though. I think that when this technology is able to make money for airlines, then medicine will have improved enough to accommodate the associated risks. (Hopefully    as treatment seems to be more lucrative for health professionals than prevention...)

Quoting FlyMatt2Bermud (Thread starter):
Some like the idea others hate it

As I stated, I love the idea. However, I hope you don't make your co-captain wear the 02 mask the whole time! This would probably be my only drawback to climbing that high, if my aircraft had the performance. If the CA always makes the FO wear the mask, then screw it. I'll request a lower altitude and cruise fast. But, I love fuel-conscious pilots, and the parabolic flight profile and max economy cruise is wonderful, as long as the pilots respect each other. I hope that your FO was wearing the mask in the video just because you were the star!

Quoting Jambrain (Reply 45):
See James May (from BBC top gear) at FL71 in a U2

Watched it many times in the last few months, and it has always brought tears to my eyes.

Quoting DashTrash (Reply 40):
Note how much room is between stall and overspeed

That's a really nice margin for being at FL510! Awesome photos too...I'd love to see more. The C750 seems as close to a fighter with a cabin as one could get. That's a wonderful flight envelope. From what I've read, it even possesses good low speed handling characteristics too. Hello visual patterns after a parabolic FL510 Mach .92 flight.
 
ElpinDAB
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RE: FL510 Pros Vs Cons?

Wed Feb 17, 2010 8:54 am

I was actually stunned from the great difference between the flight envelopes of the C750 and Global 5000 at FL510, although, under the precise circumstances that Matt listed, the Global should be perfectly safe at FL510, as should any biz jet certified to it's given service ceiling. I think that education is the key to the safe operation of aircraft to the limits of their flight envelope. One great faux paus of high altitude ops was crew of the Pinnacle flight that crashed outside of Jeff City, MO and neglected the atmospheric conditions (and ops specs for that matter) in favor of trying to set personal records. Thankfully this was a ferry flight, and the price was their own lives and the aircraft.

[Edited 2010-02-17 00:55:30]
 
flymatt2bermud
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RE: FL510 Pros Vs Cons?

Wed Feb 17, 2010 2:04 pm

Quoting elpinDAB (Reply 52):
I was actually stunned from the great difference between the flight envelopes of the C750 and Global 5000 at FL510,

What is that margin?

Quoting elpinDAB (Reply 52):
One great faux paus of high altitude ops was crew of the Pinnacle flight that crashed outside of Jeff City, MO and neglected the atmospheric conditions (and ops specs for that matter) in favor of trying to set personal records. Thankfully this was a ferry flight, and the price was their own lives and the aircraft.

It is potentially an extremely dangerous envelope, pilots who choose to fly to those boundaries definitely need to be knowledgable with their environment.

On the Global 5000 if you slow to the midpoint speed between the Vmo and Vs1 at FL510 (with 2 hours fuel remaining and ISA), you are behind the power curve at climb thrust settings. Angle of attack increasing and speed is reducing, the only way to recover airspeed is to descend (rapidly). Pretty much the same scenario as the Pinnacle example.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
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jambrain
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RE: FL510 Pros Vs Cons?

Fri Feb 19, 2010 8:43 pm

Quoting flymatt2bermud (Reply 53):
On the Global 5000 if you slow to the midpoint speed between the Vmo and Vs1 at FL510 (with 2 hours fuel remaining and ISA), you are behind the power curve at climb thrust settings. Angle of attack increasing and speed is reducing, the only way to recover airspeed is to descend (rapidly). Pretty much the same scenario as the Pinnacle example.

As a non pilot I am intrigued as to what happens when at FL51 you get into trouble, presumably it is far more difficult to recover from a stall at that altitude then just to "drop the nose" and "push throttles to max" and recover, can anyone explain what it feels like to stall up there (hopefully for the sake of your SLF in a simulator!!) How quickly does a jet spin or tumble?
Jambrain
 
flymatt2bermud
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RE: FL510 Pros Vs Cons?

Fri Feb 19, 2010 10:27 pm

This is an excellent description of a stall. Look at the Deep Stall and you will see a good example of the characteristics and why.

http://en.wikipedia.org/wiki/Stall_%28flight%29

We have trained high altitude stalls in the simulator and the experience was not too unstable but you need thousands of feet of altitude for a full recovery.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
ElpinDAB
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RE: FL510 Pros Vs Cons?

Sat Feb 20, 2010 9:46 am

Hey Matt,

Sorry for not making myself more clear. I was referring to the Vmo to Vs1 margin, which you refer to in the video as "coffin corner". I would say that coffin corner is a real concern while flying at this altitude, but I interpret coffin corner to a little more extreme than this, where the Vmo to Vs1 margin becomes dangerously slim. I think that what gets alot of pilots in trouble though is overestimating the performance of their aircraft. Very few pilots have the privilege of operating an aircraft at FL510...I can think of the Globals, C750, and LJ31 off the top of my head... But you brought up a very good point with the exponentially degrading performance of the back side of the power curve. Essentially, your flight envelope at FL510 is limited to the mid-side of the "margin" to your Vmo. But, also keep in mind the potential for turbulence at high altitudes with narrow flight envelopes. Airline dispatchers plan for this. Turbulence can increase G-loading on the airframe, and thus increase stall speed, which would further narrow your envelope. Thankfully, you are performance limited in the Global 5000, and the increased G-loading probably wouldn't increase your stall speed beyond the speed that you need to carry to remain on the positive performance side of the power curve.

By the way, I'm not criticizing your altitude choice at all. You seem like a highly competent pilot who is far more qualified than I am, although I've studied high altitude flight on my own and through organized education extensively. Keep flying at FL510 when you can!

Quoting flymatt2bermud (Reply 53):
What is that margin?

And, just to add... I've never flown either your equipment or the C750, but apparently, the C750's Vmo is Mach .92, and 220KIAS under the conditions of DashTrash's photos, with a Vs1 of less than 150 from the photo, and listed as 123KIAS at MTOW by charts I found online. The Global's is Mach .89 and 198KIAS, as labeled on your video. Vs1 is labelled at 162KIAS. Since I haven't flown your equipment and don't possess the manuals, I can't say what's true or not, but this is what I have taken from the given info and flight conditions. This seems like a huge difference to me. All accounts of the C750 that I've seen have claimed that it performs like none other above FL350. It was specifically designed to operated at high speeds and altitudes. The Global is one of the few passenger jets that can climb to such high altitudes though, and it was certified to FL510 for a reason: because the FAA found that it could safely operate there under certain conditions. Just to reiterate though, I still think that you and your pax are perfectly fine in the Global at FL510. Keep it up! I would trust you with my family or anybody else that I know. Your seem like a good pilot, and as I said, far more qualified than I am.
 
Mir
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RE: FL510 Pros Vs Cons?

Sat Feb 20, 2010 11:11 am

Quoting JamBrain (Reply 54):
As a non pilot I am intrigued as to what happens when at FL51 you get into trouble, presumably it is far more difficult to recover from a stall at that altitude then just to "drop the nose" and "push throttles to max" and recover, can anyone explain what it feels like to stall up there (hopefully for the sake of your SLF in a simulator!!) How quickly does a jet spin or tumble?

Having done several high altitude stalls in a sim, I can say that they really are non-events if you recover properly. The recovery is the same as a stall at low altitude - full power and let the nose come down - but it will take a lot longer, and you'll lose several thousand feet in the process as opposed to only one or two hundred. If you try and maintain altitude in the recovery the way you're taught to at low altitude, you'll get yourself into a world of trouble.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
flymatt2bermud
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RE: FL510 Pros Vs Cons?

Mon Feb 22, 2010 3:24 am

I was actually stunned at the great difference between the flight envelopes of the C750 and Global 5000 at FL510, although, under the precise circumstances that Matt listed, the Global should be perfectly safe at FL510. I will be interested to see ho

Quoting Mir (Reply 57):
apparently, the C750's Vmo is Mach .92, and 220KIAS under the conditions of DashTrash's photos, with a Vs1 of less than 150 from the photo, and listed as 123KIAS at MTOW by charts I found online. The Global's is Mach .89 and 198KIAS, as labeled on your video. Vs1 is labeled at 162KIAS.

Can anyone give some specific numbers on the C750 margins at FL510?
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
DashTrash
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RE: FL510 Pros Vs Cons?

Mon Feb 22, 2010 4:25 am

Quoting elpinDAB (Reply 51):
From what I've read, it even possesses good low speed handling characteristics too.

Not really. That's the trade off for the high speed / altitude capability, and the reason for the slats. It's fairly squirrly, but not as bad the older Lears.

Quoting JamBrain (Reply 54):
As a non pilot I am intrigued as to what happens when at FL51 you get into trouble, presumably it is far more difficult to recover from a stall at that altitude then just to "drop the nose" and "push throttles to max" and recover, can anyone explain what it feels like to stall up there (hopefully for the sake of your SLF in a simulator!!)

You just don't let the airplane get to that point. High risk of flame outs up there if you disrupt the airflow through the engines during a stall.

Quoting ElpinDAB (Reply 56):
All accounts of the C750 that I've seen have claimed that it performs like none other above FL350.

It performs extremely well between 35 and 45. It pigs out above and below.

Quoting flymatt2bermud (Reply 58):
Can anyone give some specific numbers on the C750 margins at FL510?

What numbers are you looking for?
 
flymatt2bermud
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RE: FL510 Pros Vs Cons?

Mon Feb 22, 2010 1:55 pm

Quoting DashTrash (Reply 59):
Quoting flymatt2bermud (Reply 58):
Can anyone give some specific numbers on the C750 margins at FL510?

What numbers are you looking for?


Actually instrument readouts of the C750 at FL510. I know the C750 has a Vmo of M.92 but that is not it's limit at FL510.

EDIT: O.K. I just found your photo with the red line at 220 KIAS. What it the highest IAS you have seen at FL510 with the C750?

[Edited 2010-02-22 06:05:25]
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
DashTrash
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RE: FL510 Pros Vs Cons?

Mon Feb 22, 2010 11:37 pm

Quoting flymatt2bermud (Reply 60):
EDIT: O.K. I just found your photo with the red line at 220 KIAS. What it the highest IAS you have seen at FL510 with the C750?

Maybe 195. The airplane won't accelerate up there, so whatever speed you level off with is what you're stuck with.
 
flymatt2bermud
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RE: FL510 Pros Vs Cons?

Wed Mar 03, 2010 10:04 pm

Quoting DashTrash (Reply 61):

Maybe 195. The airplane won't accelerate up there, so whatever speed you level off with is what you're stuck with.

The Global needs to be down to about 2:45 fuel remaining to get to FL510. It will accelerate to close to Vmo which at that ALT is approx M.855.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
Max Q
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RE: FL510 Pros Vs Cons?

Sun Mar 07, 2010 6:26 pm

Quoting DashTrash (Reply 40):

Interesting tidbit, the X has an emergency descent mode. If cabin altitude goes above 15000 with the airplane above 30,000 and the autopilot on, the airplane will make a 90 degree turn and descend at Mmo / Vmo until it gets to (I think) 15,000.

Interesting, what happens if you are over the Himalayas with numerous mountains higher than 15000' ? !
The best contribution to safety is a competent Pilot.


GGg
 
tdscanuck
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RE: FL510 Pros Vs Cons?

Sun Mar 07, 2010 8:48 pm

Quoting Max Q (Reply 63):
Interesting, what happens if you are over the Himalayas with numerous mountains higher than 15000' ? !

You hit the mountains, unless you've got a EGPWS system that's capable of actually commanding the flight controls. Hopefully, the flight crew regains consciousness and gets on O2 before that happens.

Keep in mind, if the cabin altitude has gone above 15,000 and the autopilot has remained engaged without a command, then the flight crew is unconscious anyway...it's just a matter of which piece of dirt you're going to hit.

Tom.
 
Max Q
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RE: FL510 Pros Vs Cons?

Mon Mar 08, 2010 12:15 am

Quoting tdscanuck (Reply 64):
You hit the mountains, unless you've got a EGPWS system that's capable of actually commanding the flight controls. Hopefully, the flight crew regains consciousness and gets on O2 before that happens.

Keep in mind, if the cabin altitude has gone above 15,000 and the autopilot has remained engaged without a command, then the flight crew is unconscious anyway...it's just a matter of which piece of dirt you're going to hit.

Once again, too much automation, in an attempt to 'Pilot Proof' the Aircraft you end up with a system that can get you into more harm than it is trying to protect you from !
The best contribution to safety is a competent Pilot.


GGg
 
tdscanuck
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RE: FL510 Pros Vs Cons?

Mon Mar 08, 2010 12:28 am

Quoting Max Q (Reply 65):
Once again, too much automation, in an attempt to 'Pilot Proof' the Aircraft you end up with a system that can get you into more harm than it is trying to protect you from !

I'm not following you...if you have an un-automated airplane (vis a vis cabin altitude) and you decompress the cabin to greater than 15000' and the flight crew doesn't wake up, they're not going to wake up later and the plane is going to crash.

With the X system, if the flight crew is incapacitated the autopilot will take them down to an altitude where they should regain consciousness. There is a very very small chance that you're in some part of the world where the terrain is higher than that *and* you are unlucky enough to intersect with one of the high peaks, but even then the worst case is the same as if you didn't have the automation...crash.

It sounds like, without the automation, you're guaranteed to crash if the preceding events take place. With the automation, you've got a pretty descent chance of waking up, and your worst case is no worse than if you didn't have the automation. So how is that *more* harm than it's trying to protect you from?

Tom.
 
flymatt2bermud
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RE: FL510 Pros Vs Cons?

Fri Mar 19, 2010 4:57 pm

I agree with you Tom, tis better to have the automation and chance someone will regain useful conscious than not.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
Mir
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RE: FL510 Pros Vs Cons?

Fri Mar 19, 2010 5:48 pm

Quoting tdscanuck (Reply 64):
You hit the mountains, unless you've got a EGPWS system that's capable of actually commanding the flight controls.

Since terrain databases are commonplace these days, how difficult would it be to use said databases to limit descents. Hell, all you'd really have to do is use the quadrant MSAs off the charts and not let the airplane descend below those.

Though I do agree that even without said protections, an automatic descent function is a very good protection to have.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
tdscanuck
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RE: FL510 Pros Vs Cons?

Fri Mar 19, 2010 10:56 pm

Quoting Mir (Reply 68):
Since terrain databases are commonplace these days, how difficult would it be to use said databases to limit descents.

Implement just this function isn't particularly difficult, especially on a FBW airliner. However, certifying it is a whole different matter because now you've got a non-flight controls computer with override authority on the flight controls. There would be a lot of knock on effect, including:
-really foolproof logic to differentiate between when you want to descent (e.g. landing) and when you don't
-protection against bad terrain data
-elevating the GPWS to the same safety criticality as the flight controls (big certification and testing costs)
-adding a bunch of new potential failure modes to the flight controls

It's doable, but I'm not sure the cost/complexity would be worth it.

Tom.
 
DashTrash
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RE: FL510 Pros Vs Cons?

Sat Mar 20, 2010 4:14 am

Quoting tdscanuck (Reply 69):
-adding a bunch of new potential failure modes to the flight controls

I might not have mentioned the EDM is an autopilot feature. It has to be on for the X to descend itself.
 
flymatt2bermud
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RE: FL510 Pros Vs Cons?

Sat Mar 20, 2010 11:33 am

Quoting tdscanuck (Reply 69):
It's doable, but I'm not sure the cost/complexity would be worth it.

Especially when you consider the chances of an actual rapid decompression event at altitude.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci

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