Boeing 787-9 Twin Jet Dreamliner Hits Top Speed of 801 MPH

Mohonri

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What happens when they unexpectedly leave the stream going higher than Mach1 in a plane not designed for that?
The border between the jetstream and the air below isn't a sharp cutoff, so no issues.
 

sfsuphysics

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What if the treadmill was on the plane, but the observer was in a submarine, would it be mach 1 underwater? :ROFLMAO:;)
Well to a stationary point above Earth everyone standing on the ground through the US is going mach 1!
 
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zauber

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The FAA limits how fast a commercial jet can go with passengers on board as there are safely guidelines and of course impact on other jets flying in succession on the same flight path.

The only speed limits in class A airspace are 250 knots IAS below 10,000 feet and not to exceed Mach 1 over the continental Unites States. With or without passengers. Airspeeds may be assigned by ATC to manage traffic flow.
 

focbde

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Problem is it's not the flow separation that cause the high speed stall, it is the shockwave caused by supersonic airflow above wings. For low-speed stall we pitch down to reduce the angle of attack (angle between the aircraft pitch and the flight path) and increase airspeed to regain lift but for high speed stall the only option is to use speed brake to reduce airspeed as pitching down will worsen the stall. It's best to recognize the stall early and make recovery actions because once you are in a deep stall with a descend rate over 10 000ft/ min, chances of recovery is pretty slim.

The flow separation is however caused by the shockwave... hence 'shock-induced separation'. Speed brakes at that velocity are not an option - they'll be torn off. Powering back and natural drag will reduce airspeed VERY rapidly at that velocity... it's like flying through treacle in terms of friction.
 

Krizby

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The flow separation is however caused by the shockwave... hence 'shock-induced separation'. Speed brakes at that velocity are not an option - they'll be torn off. Powering back and natural drag will reduce airspeed VERY rapidly at that velocity... it's like flying through treacle in terms of friction.

Shockwave not only cause flow separation but also increase the air pressure above wings, causing a nose down moment (Mach Tuck), even at idle power the airspeed would still increase causing further pitch down moment. Once the aircraft has lost sufficient altitude (a lot) so that shockwave is not happening then the aircraft can recover.

Well I don't know if you are a pilot or which aircraft you fly but any flight control surface will be torn off at speed way before speed brakes do, and we are supposed to extend speed brake immediately before reaching Mmo/Vmo (reduce power rapidly can cause a nose down moment that may worsen the situation), and pitching down for example -5 degrees will accelerate the aircraft at idle power without any speed brakes, imaging pitching down -45 degree (Boeing call that Unusual attitude recovery and we were trained in the Simulator for that)
 
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focbde

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Shockwave not only cause flow separation but also increase the air pressure above wings, causing a nose down moment (Mach Tuck), even at idle power the airspeed would still increase causing further pitch down moment. Once the aircraft has lost sufficient altitude (a lot) so that shockwave is not happening then the aircraft can recover.

Well I don't know if you are a pilot or which aircraft you fly but any flight control surface will be torn off at speed way before speed brakes do, and we are supposed to extend speed brake immediately before reaching Mmo/Vmo (reduce power rapidly can cause a nose down moment that may worsen the situation), and pitching down for example -5 degrees will accelerate the aircraft at idle power without any speed brakes, imaging pitching down -45 degree (Boeing call that Unusual attitude recovery and we were trained in the Simulator for that)

Going a bit too in-depth for this thread I'd say, but yes - pilot. :) I disagree that a -5 degree attitude at speeds around Mach .8 with engines at idle will accelerate the aircraft simply due to drag, but we can just agree to disagree and leave it there.
 

Olle P

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Well any commercial aircraft will experience high speed stall way before reaching Mach 1 though, that means the aircraft lose all lift and falling like a rock, ...
You clearly underestimate the flight characteristics of rocks...
If you lose aerodynamic lift you go ballistic, continuing at the same speed horizontally while beginning a gravitational descent.
Add engines that provide some lift and speed to the rock and it will fly quite nicely...
 

Olle P

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What if the treadmill was on the plane, but the observer was in a submarine, would it be mach 1 underwater? :ROFLMAO:;)
Given that the speed of sound under water is about 1,500 m/s (3,350 mph) I'd say no, not really...
 
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kju1

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You clearly underestimate the flight characteristics of rocks...
If you lose aerodynamic lift you go ballistic, continuing at the same speed horizontally while beginning a gravitational descent.
Add engines that provide some lift and speed to the rock and it will fly quite nicely...

And its all moot becuase their airspeed wasnt that it was their GROUNDSPEED.
 
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The only speed limits in class A airspace are 250 knots IAS below 10,000 feet and not to exceed Mach 1 over the continental Unites States. With or without passengers. Airspeeds may be assigned by ATC to manage traffic flow.

Oops sorry that is company policy, not FAA, well technically it is FAA because the airline makes it a policy so if violated the FAA will fine the company under the proceedings and proceedures or operations manual submitted to them, hence my confusion. Quoted and explained by a pilot. A ferry flight with no passengers is specified as an exception. It's like DG regulations where's you have IATA and FAA standards but then policies set forth are forcefully mandated.
 

kju1

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The only speed limits in class A airspace are 250 knots IAS below 10,000 feet and not to exceed Mach 1 over the continental Unites States. With or without passengers. Airspeeds may be assigned by ATC to manage traffic flow.

Your statement is incorrect. Class A airspace starts at 18,000 feet MSL and requires all aircraft to be operating under IFR. Here are the actual regulatory speed limits from FAR 91.1, 91.117, 91.703 and AIM 4-4-12:

  • In the United States — Mach 1
  • 10,000 feet msl or above — Unrestricted (but not more than Mach 1)
  • Below 10,000 feet msl — 250 kias
  • Class B airspace — Unrestricted at or above 10,000 feet msl, 250 kias below 10,000 feet msl
  • Beneath Class B or in VFR corridor through Class B — 200 kias
  • Procedure turn — 200 kias
  • Class C or D airspace (at or below 2,500 feet agl within 4 nm of the primary airport) — 200 kias (unless a higher speed is specifically approved by ATC)

Note that 91.117(d) specifically states that if the aircraft's minimum speed is HIGHER than any of those published limits than the aircraft's minimum safe controllable speed is the limit. There is no regulatory requirement to inform ATC when operating at said speed either. Additionally except for the class C/D restrictions ATC CANNOT assign you a speed faster than the limit - they have no authority to waive a regulation 91.117(a).

Note that the 250 kias below 10,000 feet msl speed restriction does not apply to aircraft operating beyond 12 nm from the coastline (i.e. outside of the ADIZ).

Oops sorry that is company policy, not FAA, well technically it is FAA because the airline makes it a policy so if violated the FAA will fine the company under the proceedings and proceedures or operations manual submitted to them, hence my confusion. Quoted and explained by a pilot. A ferry flight with no passengers is specified as an exception. It's like DG regulations where's you have IATA and FAA standards but then policies set forth are forcefully mandated.

Correct if you are a 121, charter operation, 141 flight school etc then FAA approved policies effectively become regulations for those operations. They arent actually regulations but they are enforced with the full weight of regulations and pilots found violating them can be subject to FAA enforcement actions (most likely the company will face a fine though).
 

Krizby

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Going a bit too in-depth for this thread I'd say, but yes - pilot. :) I disagree that a -5 degree attitude at speeds around Mach .8 with engines at idle will accelerate the aircraft simply due to drag, but we can just agree to disagree and leave it there.

Let me guess, you are flying turbo prop aircraft ain't ya, turbo jets flying charateristics are a little different. Every flight we descend with idle power, +1 degree pitch and maintain M.85/ 325kt IAS, simply pitching down to -5 degree will get us to Mmo/Vmo in a couple of seconds.
 

focbde

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Let me guess, you are flying turbo prop aircraft ain't ya, turbo jets flying charateristics are a little different. Every flight we descend with idle power, +1 degree pitch and maintain M.85/ 325kt IAS, simply pitching down to -5 degree will get us to Mmo/Vmo in a couple of seconds.

No I don't fly turboprops. It's true that descents are normally performed under idle power unless expedited, but from an already reduced airspeed and thus massively reduced drag level, as drag levels increase exponentially with airspeed. What you're trying to tell me is that there is little to no wind drag decelerating the crate when you're already at .8 - and that a nose-down attitude of -5 degrees will, even though you're already at .8 and throttled back, not reduce airspeed.

Well OK then. As I said, best leave it there :)
 

ManofGod

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Going a bit too in-depth for this thread I'd say, but yes - pilot. :) I disagree that a -5 degree attitude at speeds around Mach .8 with engines at idle will accelerate the aircraft simply due to drag, but we can just agree to disagree and leave it there.

You cannot agree to disagree because that is not the way flight dynamics work. Just like computers, it is an either or situation, not a whatever situation.
 

focbde

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You cannot agree to disagree because that is not the way flight dynamics work. Just like computers, it is an either or situation, not a whatever situation.

Couldn't agree more with you, however I have my understanding of how the physics would work in that scenario, and if someone thinks I'm wrong, it's their right, and I don't think it's then required or necessary of me to force them around to my point of view.
 

ManofGod

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Couldn't agree more with you, however I have my understanding of how the physics would work in that scenario, and if someone thinks I'm wrong, it's their right, and I don't think it's then required or necessary of me to force them around to my point of view.

Force them no but, if you both flying the same craft in the same conditions performing the same maneuvers, you should be more or less operating in the same way.
 
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Wow it's really cool these people that were on this flight get to say they went mach 1 not many people can say that.
 

YeuEmMaiMai

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yawn let me know when it can get close to Mach 1 on its' own... you know like the 747 which has the ability to cruise at Mach .92
 

Mohonri

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Guys, the plane didn't break mach 1. Mach number has nothing to do with ground speed.
 

Krizby

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Couldn't agree more with you, however I have my understanding of how the physics would work in that scenario, and if someone thinks I'm wrong, it's their right, and I don't think it's then required or necessary of me to force them around to my point of view.

Hah so the discussion was still going ? oh well let me point out the flaws in your understanding of physics or the basic of flying:

To control your airspeed first is pitch then power, that means the pitch control has instantaneous control over airspeed, power come in slower. You can try this in your aircraft or in simulator : quickly pitch down to -5 degree and see how fast airspeed increase; second scenario quickly retard the power and see how slow the airspeed decrease (the nose will come down initially and airspeed will maintain for a couple of second before decreasing). All I'm saying is when an aircraft experience a pitch down moment, it's airspeed will always increase initially regardless. I only have like 6000h flying A321, B777, B787 but never once did I pitch down to -5 degree in a controlled descend. My approximate calculation at -5 degree pitch at M .85 with idle power, the A/C will descend at 5500-6000ft/min, highly doubt drag is enough to prevent the A/C from speeding up (unless you go to reverse on Turbo Prop, Turbo Jets has ground/air logics to prevent reverser in flight).
For more information just go to wikipedia and type in Mach Tuck and see how dangerous that is for subsonic aircrafts.
 

ManofGod

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Hah so the discussion was still going ? oh well let me point out the flaws in your understanding of physics or the basic of flying:

To control your airspeed first is pitch then power, that means the pitch control has instantaneous control over airspeed, power come in slower. You can try this in your aircraft or in simulator : quickly pitch down to -5 degree and see how fast airspeed increase; second scenario quickly retard the power and see how slow the airspeed decrease (the nose will come down initially and airspeed will maintain for a couple of second before decreasing). All I'm saying is when an aircraft experience a pitch down moment, it's airspeed will always increase initially regardless. I only have like 6000h flying A321, B777, B787 but never once did I pitch down to -5 degree in a controlled descend. My approximate calculation at -5 degree pitch at M .85 with idle power, the A/C will descend at 5500-6000ft/min, highly doubt drag is enough to prevent the A/C from speeding up (unless you go to reverse on Turbo Prop, Turbo Jets has ground/air logics to prevent reverser in flight).
For more information just go to wikipedia and type in Mach Tuck and see how dangerous that is for subsonic aircrafts.

This is pretty accurate because if you think of it as a landing, whether on land or sea, pitch controls air speed and throttle controls altitude. (I am not a pilot but, some of the simulators that I have flown on the PC are incredibly detailed and life like.) Also, I physically read some stuff about it and it makes sense. If anyone disagrees, please see the flight 3407 crash in Buffalo on February of 2009, the pilot pulled back and stalled the plane because he killed his airspeed. :(
 

YeuEmMaiMai

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Hah so the discussion was still going ? oh well let me point out the flaws in your understanding of physics or the basic of flying:

To control your airspeed first is pitch then power, that means the pitch control has instantaneous control over airspeed, power come in slower. You can try this in your aircraft or in simulator : quickly pitch down to -5 degree and see how fast airspeed increase; second scenario quickly retard the power and see how slow the airspeed decrease (the nose will come down initially and airspeed will maintain for a couple of second before decreasing). All I'm saying is when an aircraft experience a pitch down moment, it's airspeed will always increase initially regardless. I only have like 6000h flying A321, B777, B787 but never once did I pitch down to -5 degree in a controlled descend. My approximate calculation at -5 degree pitch at M .85 with idle power, the A/C will descend at 5500-6000ft/min, highly doubt drag is enough to prevent the A/C from speeding up (unless you go to reverse on Turbo Prop, Turbo Jets has ground/air logics to prevent reverser in flight).
For more information just go to wikipedia and type in Mach Tuck and see how dangerous that is for subsonic aircrafts.
or you can ask the Fed-EX pilot that took at DC10-30 fully loaded cargo plane supersonic.. he clearly describes what you are taking about as the plane entered into Mach tuck... witnesses on the ground stated he was flying that thing as though it was a fighter jet...and that was AFTER he got beat down by the dude in the jump seat...
 

kju1

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Hah so the discussion was still going ? oh well let me point out the flaws in your understanding of physics or the basic of flying:

To control your airspeed first is pitch then power, that means the pitch control has instantaneous control over airspeed, power come in slower. You can try this in your aircraft or in simulator : quickly pitch down to -5 degree and see how fast airspeed increase; second scenario quickly retard the power and see how slow the airspeed decrease (the nose will come down initially and airspeed will maintain for a couple of second before decreasing). All I'm saying is when an aircraft experience a pitch down moment, it's airspeed will always increase initially regardless. I only have like 6000h flying A321, B777, B787 but never once did I pitch down to -5 degree in a controlled descend. My approximate calculation at -5 degree pitch at M .85 with idle power, the A/C will descend at 5500-6000ft/min, highly doubt drag is enough to prevent the A/C from speeding up (unless you go to reverse on Turbo Prop, Turbo Jets has ground/air logics to prevent reverser in flight).
For more information just go to wikipedia and type in Mach Tuck and see how dangerous that is for subsonic aircrafts.

Any novice pilot should know pitch for airspeed and then power. ;) Even in normally aspirated aircraft a power change is slower to affect airspeed than a pitch change (albeit faster than in a jet). Its always comical when I take a new student up and demonstrate how I can make the plane stall with full power in. And even funnier (sadly) when i demonstrate to an experienced pilot how to stall the plane at a stall speed that is much higher than what is published in the book.

They just dont teach about angle of attack and energy management in a lot of flight schools anymore :(. Maybe its because basic physics is "too hard" for most people?
 

ManofGod

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Any novice pilot should know pitch for airspeed and then power. ;) Even in normally aspirated aircraft a power change is slower to affect airspeed than a pitch change (albeit faster than in a jet). Its always comical when I take a new student up and demonstrate how I can make the plane stall with full power in. And even funnier (sadly) when i demonstrate to an experienced pilot how to stall the plane at a stall speed that is much higher than what is published in the book.

They just dont teach about angle of attack and energy management in a lot of flight schools anymore :(. Maybe its because basic physics is "too hard" for most people?

If that last part is true, then I am glad I do not like flying anymore. (Have not been on a flight since 1991 and no way I would be on one where a pilot does not understand basic flight dynamics, which those two thing you mentioned are a part of.)
 

kju1

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If that last part is true, then I am glad I do not like flying anymore. (Have not been on a flight since 1991 and no way I would be on one where a pilot does not understand basic flight dynamics, which those two thing you mentioned are a part of.)

I would say a good 50% of my "advanced" (meaning seeking commercial or ATP) students do not understand these principals. Roughly the same for the pilots I give BFRs (biennial flight reviews) to. I havent actually been gathering statistics but it is a general trend I have been noticing. I always ask pilots I review where they were taught and the flight academys seem to be the worst offenders (unless they are military). I dont know if they arent actually teaching that curriculum of course but I do notice a lack of knowledge and very poor stick and rudder skills from those pilots. My experience with them has shown me they are more likely to be button pushers on the GPS and autopilot moreso than anything else.

Thats not to say military pilots are perfect either. I once had a 20 yr military vet and current ATP doing a check out in a local club I do check outs for in my spare time. He showed such a lack of understanding of FAA regulations that I not only failed him on the checkout but I went so far as to write "needs recurrent training in FAA regulations and basic aircraft maneuvers" in his logbook and had a nice chat with his superior at work. I later heard they made him do a proficiency check and he failed that too. So thankfully we got him off the flight line.

I also dont like flying in an airliner but thankfully I just fly myself most places.
 

YeuEmMaiMai

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given how many airbus pilots crashed due to not understanding how the plane works is scary... france flight 411 rings a bell... push nose down, gain speed, come out of stall...
 

Olle P

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And its all moot becuase their airspeed wasnt that it was their GROUNDSPEED.
Not in Krizby's example that I was referring to.

Any novice pilot should know pitch for airspeed and then power. ... a power change is slower to affect airspeed than a pitch change...
Yes, and that's because with a change in pitch you initially trade speed for altitude.
If the objective is to change speed while maintaining altitude you first change the power setting and then adjust the pitch to compensate for the change in lift.
 

kju1

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given how many airbus pilots crashed due to not understanding how the plane works is scary... france flight 411 rings a bell... push nose down, gain speed, come out of stall...

From my understanding the black box indicated the pitot static system was clogged with ice. The Airbus jets are electronic flight controls so I am not sure the pilot would "feel" the buffet. Caveat I have not flown any Airbus aircraft so I dont know for sure. But with garbage data coming in instruments wouldve been all wrong and if they were in IFR conditions there would be no visual input.

I could easily see this causing a crash because the auto pilot already had pitched the nose up too high to recover based on bad data. Then the pilots thinking they were about to stall would have pitched up even further potentially making the aircraft enter a deep stall. Deep stalls are very dangerous in that type of aircraft.

I could even see them ignoring a stall warning if it went off. People get hyper focused on things and its easy to disregard what you believe to be "incorrect" data. It doesnt even have to be an emergency for you to not believe facts when they are sitting right in front of your eyes...its called confirmation bias. We see or hear what we expect to see or hear.
 

YeuEmMaiMai

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From my understanding the black box indicated the pitot static system was clogged with ice. The Airbus jets are electronic flight controls so I am not sure the pilot would "feel" the buffet. Caveat I have not flown any Airbus aircraft so I dont know for sure. But with garbage data coming in instruments wouldve been all wrong and if they were in IFR conditions there would be no visual input.

I could easily see this causing a crash because the auto pilot already had pitched the nose up too high to recover based on bad data. Then the pilots thinking they were about to stall would have pitched up even further potentially making the aircraft enter a deep stall. Deep stalls are very dangerous in that type of aircraft.

I could even see them ignoring a stall warning if it went off. People get hyper focused on things and its easy to disregard what you believe to be "incorrect" data. It doesnt even have to be an emergency for you to not believe facts when they are sitting right in front of your eyes...its called confirmation bias. We see or hear what we expect to see or hear.
does not negate the fact that they did not have a basic understanding of how the plane worked.

They took an instructor pilot and placed him into the simulator and recreated the conditions that lead up to said crash, the only thing that guy did was set power to 77% and nose up slightly to maintain level flight. You can watch the video on Youtube under Mayday


The stall alarm was telling them that they were in deep dodo for quite some time and instead of pushing the nose down to gain airspeed they (junior pilot) was pulling back on said stick entire time as you hear STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! STALL! TERRAIN! STALL! TERRAIN! STALL! TERRAIN STALL! and the plane hit the ocean flat on it's bottom...
 

zauber

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zauber said:
Your statement is incorrect. Class A airspace starts at 18,000 feet MSL and requires all aircraft to be operating under IFR. Here are the actual regulatory speed limits from FAR 91.1, 91.117, 91.703 and AIM 4-4-12:

  • In the United States — Mach 1
  • 10,000 feet msl or above — Unrestricted (but not more than Mach 1)
  • Below 10,000 feet msl — 250 kias
  • Class B airspace — Unrestricted at or above 10,000 feet msl, 250 kias below 10,000 feet msl
  • Beneath Class B or in VFR corridor through Class B — 200 kias
  • Procedure turn — 200 kias
  • Class C or D airspace (at or below 2,500 feet agl within 4 nm of the primary airport) — 200 kias (unless a higher speed is specifically approved by ATC)

Note that 91.117(d) specifically states that if the aircraft's minimum speed is HIGHER than any of those published limits than the aircraft's minimum safe controllable speed is the limit. There is no regulatory requirement to inform ATC when operating at said speed either. Additionally except for the class C/D restrictions ATC CANNOT assign you a speed faster than the limit - they have no authority to waive a regulation 91.117(a).

Note that the 250 kias below 10,000 feet msl speed restriction does not apply to aircraft operating beyond 12 nm from the coastline (i.e. outside of the ADIZ).



Correct if you are a 121, charter operation, 141 flight school etc then FAA approved policies effectively become regulations for those operations. They arent actually regulations but they are enforced with the full weight of regulations and pilots found violating them can be subject to FAA enforcement actions (most likely the company will face a fine though).

Sorry my statement actually combined the limits for Class A and Class E airspace, which is what I work at ZNY. There are radar approach controls below the entirety of the airspace I work, so I never deal with Class B, C, D, or G airspace.
 
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