FL430 for commercial airliners

[twa22]

This is something I've been wondering for a while, but I wanted to ask why only few operators in the world fly at FL430. Most Boeing and Airbus aircraft have a service ceiling of FL430, and now with many 787s and a350s around, it's a more common sight around the globe, but I've never seen a North American operator at these altitudes. I know the likes of a 777 or a 747 altitude is generally restricted due to weight, while 787s and a350s not so much. I'm sure there's a lot more technical and operational things involved, such as oceanic crossing assigned altitudes, and others which I am not familiar with, but I'm genuinely curious why more operators don't opt to fly a 430 if their planes are capable...

[fish4life]

I think (may be mistaken) above 410 one pilot has to have O2 on at all times. Would the drop down masks only be approved for 410 in that case as well on those aircraft?

[twa22]

Ah that makes sense, I didn't even think about that... did a quick google search and found the FAR reference, which i'm sure the CARS one is likely the same

https://rgl.faa.gov/Regulatory_and_Guid ... enDocument

Now what I would be curious to know is, in other parts of the world where a few operators go up to FL430 on the daily, and stay there for hours, I wonder if the mask rule applies

[jpilot77]

It is exactly because you’d have one of the 2 pilots always on oxygen. Also the good old 767 could get up 430 as well.

[matt foley]

Every aircraft will have an optimum and a maximum alt showing on the FMS. These altitudes vary with weight and environmental conditions but an example might be "Optimum FL377 MAX FL401". I have no idea about the most modern types you describe but it would be very unusual to have an optimum above FL400 in a 67/57/37 etc. Very light and looking to go over some weather or a more direct routing in otherwise congested airspace would give a reason to go above optimum but when you do a host of other issues arise ie stall speed and VMO get very close and you are one pocket of turbulence away for being to fast or not fast enough. Higher isn't always better.

MF

[Cessna 180]

Because 430 isn't an RVSM altitude. You would need a block altitude to operate at FL430.

[NotDirty!]

Because 430 isn't an RVSM altitude. You would need a block altitude to operate at FL430.

It is non-RVSM, but you don’t require a block altitude... it is simply the next available level above 410, so it is actually a westbound altitude. 450 would be the next available eastbound altitude.

[DHC-1 Jockey]

What about biz jets? They’re routinely above 410, even up into the FL500’s.

Do one of those pilots need to be on oxygen at all times as well?

[digits_]

What about biz jets? They’re routinely above 410, even up into the FL500’s.

Do one of those pilots need to be on oxygen at all times as well?

Yes.


In theory.

[lhalliday]

I've always wondered about Concorde in this respect, either the regulations were different or there were things we just didn't see on the flight deck.

They also would have had ITAR issues with GPS navigation, but GPS wasn't a big thing in planes until after they were retired.

...laura

[ahramin]

ITAR?

[Rockie]

Several transport category planes are certified above FL410 and can reach it weight and environmental conditions permitting, but as mentioned the regulation (605.32 (3)(b)) requires one crew member to wear a mask above FL410. It's due to the time of useful consciousness in the event of an explosive decompression, and I know pilots would love to have that rule changed but unless they can figure out how to increase a human body's TOC I don't see that happening anytime soon. There's not much benefit operating at 430 versus 410 to offset the PITA of wearing the mask full time which is why you don't see it, plus you'd be using up the crew O2 for normal ops instead of emergency and the aircraft bottles aren't that big.

[lhalliday]

ITAR?

International Traffic in Arms Regulations. Law that says (among other things) that GPS receivers that will work above specified speeds (1000 knots) or altitudes (FL600) are sensitive products that require export approval. The intent was to make it impossible for bad guys to use them in guided missiles and such. It makes other things awkward, like using GPS on satellites.

...laura

[New Antique Pilot]

I've always wondered about Concorde in this respect, either the regulations were different or there were things we just didn't see on the flight deck.

They also would have had ITAR issues with GPS navigation, but GPS wasn't a big thing in planes until after they were retired.

...laura

I had a short cockpit visit on the Concorde on a flight from LHR-JFK-OSH in 1985.
We were up around FL600 and no one was wearing a O2 mask.

NAP

[FL030]

Around 4 seconds of useful consciousness.

[NotDirty!]

I've always wondered about Concorde in this respect, either the regulations were different or there were things we just didn't see on the flight deck.

They also would have had ITAR issues with GPS navigation, but GPS wasn't a big thing in planes until after they were retired.

...laura

I had a short cockpit visit on the Concorde on a flight from LHR-JFK-OSH in 1985.
We were up around FL600 and no one was wearing a O2 mask.

NAP

I don’t suppose that the CARs (or ANOs in 1985) apply to a UK based airline flying to the USA.

IIRC the FARs have more restrictive O2 rules below 410, something about the PF had to don his/her mask if the other pilot left the flight deck above ~250.

Someone has said that O2 regs are probably the most frequently intentionally violated rules in the book. That doesn’t make it right, but not surprising.

[North Shore]

I had a short cockpit visit on the Concorde on a flight from LHR-JFK-OSH in 1985.
We were up around FL600 and no one was wearing a O2 mask.

NAP

What a magnificent bird! Higher, and faster, than many/most of the fighter planes at the time! And, hella sexy looking, too!

[bobcaygeon]

I've always wondered about Concorde in this respect, either the regulations were different or there were things we just didn't see on the flight deck.

They also would have had ITAR issues with GPS navigation, but GPS wasn't a big thing in planes until after they were retired.

...laura

I had a short cockpit visit on the Concorde on a flight from LHR-JFK-OSH in 1985.
We were up around FL600 and no one was wearing a O2 mask.

NAP

1985........They wouldn't wear masks because that would interrupt the chain smoking....

Air France was still serving their pilots wine with their crew meals on transatlantic flights and we de-iced with hot water (or not at all)

[twa22]

I've always wondered about Concorde in this respect, either the regulations were different or there were things we just didn't see on the flight deck.

They also would have had ITAR issues with GPS navigation, but GPS wasn't a big thing in planes until after they were retired.

...laura

I had a short cockpit visit on the Concorde on a flight from LHR-JFK-OSH in 1985.
We were up around FL600 and no one was wearing a O2 mask.

NAP

I don’t suppose that the CARs (or ANOs in 1985) apply to a UK based airline flying to the USA.

IIRC the FARs have more restrictive O2 rules below 410, something about the PF had to don his/her mask if the other pilot left the flight deck above ~250.

Someone has said that O2 regs are probably the most frequently intentionally violated rules in the book. That doesn’t make it right, but not surprising.

This is what I would like to know as well. As I have mentioned in one of my previous posts, if one looks up flights on flightradar24, you will notice that quite a few airlines outside North America frequently operate at FL430, and some flights for the duration of the entire flight. For example, there are a few BA99 flights from LHR to YYZ at the beginning of January that operated the entire flight at FL430... This was when the restrictions on the UK were announced, so likely no pax and just cargo

Either way, not really that important, just merely curious

[BMLtech]

I remember reading somewhere back in the day that the reason the Concorde had such small cabin windows was that it was designed with enough pack flow to maintain partial pressurization with one cabin window blown out so that the pax blood would not boil. Crazy windy I bet. Wonder if they ever demonstrated it during certification? Would also be interesting to know what the emergency descent procedure was.How would they control the G loads in a pushover at Mach 2?