ROP and LOP as related to "the feel"

[Pinecone]

No, not exactly the step.  But anyway, if you climb to your absolute service ceiling, you are at best climb, do when you cannot climb, you cannot accelerate, but you are at the max IAS you can get to, so still not a step.

And I as I mentioned, there is the edge case of the "coffin corner."   That is where Vne (TAS) and Stall speed (IAS) become the same.

If you pull up the nose you stall.  If you push the nose down, you are exceeding Vne.

One of the few planes to have deal with this is the U2.

 

[EricJ]

I know not all early J models had one, but my airplane definitely has a step.

Just off the end of the wing walk.    Mine doesn't even retract.

[N201MKTurbo]

26 minutes ago, Pinecone said:

No, not exactly the step.  But anyway, if you climb to your absolute service ceiling, you are at best climb, do when you cannot climb, you cannot accelerate, but you are at the max IAS you can get to, so still not a step.

And I as I mentioned, there is the edge case of the "coffin corner."   That is where Vne (TAS) and Stall speed (IAS) become the same.

If you pull up the nose you stall.  If you push the nose down, you are exceeding Vne.

One of the few planes to have deal with this is the U2.

 

Oh, its not that bad, I heard they usually operated with a 3 - 5 knot spread...

Luckily, the air is pretty smooth up there.

[A64Pilot]

58 minutes ago, N201MKTurbo said:

Oh, its not that bad, I heard they usually operated with a 3 - 5 knot spread...

Luckily, the air is pretty smooth up there.

Yeah, if you were in a U-2 and the missile warning went off all you could do was clinch your butt cheeks, cause you couldn’t change A/S and maneuvers had to be very gentle, like half standard rate.

[Pinecone]

Yes, they did not run it up to the absolute limit.  But a lot closer than most pilots do.

[A64Pilot]

I think modern biz jets don’t have a coffin corner anymore that was the old Lears and I’m sure some others, but as I’m no jet driver it’s all second hand

[47U]

9 hours ago, N201MKTurbo said:

Luckily, the air is pretty smooth up there.

The air is extremely smooth up there.  I was on the U-2 mx side for the last half of my career.  The air was so smooth in fact, when Lockheed updated the U-2 avionics with a glass cockpit and digital autopilot (mid ‘90s timeframe), after a couple hours of stable flight, the rudder servo would randomly kick hard and then disconnect the axis.  Understandably, the pilots did NOT like that.  We submitted a formal request for ‘engineering assistance’ and after analyzing the issue, Lockheed updated the software and the problem disappeared.  

As to turbulence, there was an orbit off the Korean peninsula that, during a certain time of year, was known for its ‘wave,’ for lack of a better term.  It was so pronounced that new pilots on their first deployment were sometimes restricted from flying that mission.  One pilot got into a wave that ultimately  exceeded the aircraft’s roll rate to recover, so what does he do?  He takes it on around and rolls the airplane, at FL70+.   At the mission debrief the intel community, recording the telemetry of the azimuth on aft datalink antenna, verified that airplane executed an aileron roll.  

Pilot’s call sign… the “Wookie.”

Apologize for the thread drift…

[N201MKTurbo]

24 minutes ago, 47U said:

The air is extremely smooth up there.  I was on the U-2 mx side for the last half of my career.  The air was so smooth in fact, when Lockheed updated the U-2 avionics with a glass cockpit and digital autopilot (mid ‘90s timeframe), after a couple hours of stable flight, the rudder servo would randomly kick hard and then disconnect the axis.  Understandably, the pilots did NOT like that.  We submitted a formal request for ‘engineering assistance’ and after analyzing the issue, Lockheed updated the software and the problem disappeared.  

As to turbulence, there was an orbit they off the Korean peninsula that, during a certain time of year, was known for its ‘wave,’ for lack of a better term.  It was so pronounced that new pilots on their first deployment were sometimes restricted from flying that mission.  One pilot got into a wave that ultimately  exceeded the aircraft’s roll rate to recover, so what does he do?  He takes it on around and rolls the airplane, at FL70+.   At the mission debrief the intel community, recording the telemetry of the azimuth on aft datalink antenna, verified that airplane executed an aileron roll.  

Pilot’s call sign… the “Wookie.”

Apologize for the thread drift…

 

 I used to work with a guy who was A U2 ground crew guy, perhaps you knew him. To bad I can’t remember his name. He told me all kinds of stories about rolling them out with all kinds of fake antennas and bulges to fake out the satellites. They would rip them all off in the run up area.

 

 

24 minutes ago, 47U said:

 

[Pinecone]

3 hours ago, A64Pilot said:

I think modern biz jets don’t have a coffin corner anymore that was the old Lears and I’m sure some others, but as I’m no jet driver it’s all second hand

ALL aircraft have a coffin corner.  Vne is TAS, Stall speed is IAS.  At SOME altitude, the two will be the same speed.

You may not have power to get to that altitude though. 

[N201MKTurbo]

4 minutes ago, Pinecone said:

ALL aircraft have a coffin corner.  Vne is TAS, Stall speed is IAS.  At SOME altitude, the two will be the same speed.

You may not have power to get to that altitude though. 

Oh, yea, my turbo J will get there. 

[Will.iam]

10 hours ago, Pinecone said:

No, not exactly the step.  But anyway, if you climb to your absolute service ceiling, you are at best climb, do when you cannot climb, you cannot accelerate, but you are at the max IAS you can get to, so still not a step.

And I as I mentioned, there is the edge case of the "coffin corner."   That is where Vne (TAS) and Stall speed (IAS) become the same.

If you pull up the nose you stall.  If you push the nose down, you are exceeding Vne.

One of the few planes to have deal with this is the U2.

 

Actually any airliner has the capability to reach coffin corner especially light weight we just don’t push for it. There is no reason / cost benefit to go there and with all the problems stated above not smart as a career choice to go experience it. 

[Pinecone]

The coffin corner for my 252 seems to be 60,000 feet.

I don't think it will make it.

Interestingly, a 737 seems to be about the same. 61,500 with Vne of MACH 0.82 and stall speed of 150

[N201MKTurbo]

6 minutes ago, Pinecone said:

The coffin corner for my 252 seems to be 60,000 feet.

I don't think it will make it.

Interestingly, a 737 seems to be about the same. 61,500 with Vne of MACH 0.82 and stall speed of 150

So, what is the MMO of your 252? VNE is irrelevant. 

[Pinecone]

Vne is Vne.  Not to exceed.  MMO is basically the same.  

The issue is, Vne is marked on the ASI as a indicated airspeed, but it is really a TAS.  So, at 60,000, an IAS of 61 equals a TAS of 196.

[Will.iam]

3 hours ago, Pinecone said:

The coffin corner for my 252 seems to be 60,000 feet.

I don't think it will make it.

Interestingly, a 737 seems to be about the same. 61,500 with Vne of MACH 0.82 and stall speed of 150

Don’t know about 737 but a tanker which is basicalky a 707 will reach coffin corner as low as 40,000ft because you are so heavy with fuel you need to go so fast to offset the weight but you can’t as you are hitting against mmo. This wasn’t an issue with the old A model engibes as they lacked the power to lift that much weight that high but with the R model engines had way more thrust able to lift it but the wings can’t generate enough lift without going past mmo. I would think the 757 would be the sanme with it’s excess thrust capacity. 

[A64Pilot]

3 hours ago, N201MKTurbo said:

So, what is the MMO of your 252? VNE is irrelevant. 

On aircraft where it’s possible I believe it’s marked by a barber pole, think another needle on the AS indicator, it’s movable because it’s not one set speed but varies on conditions 

Not that I’ve ever flown an aircraft that has a barber pole

[A64Pilot]

3 hours ago, Pinecone said:

Vne is Vne.  Not to exceed.  MMO is basically the same.  

The issue is, Vne is marked on the ASI as an indicated airspeed, but it is really a TAS.  So, at 60,000, an IAS of 61 equals a TAS of 196.

while MMO is a never exceed speed I think it’s different than VNE, VNE is very often a structural limit or a limit that the aircraft has been tested to. VNE is usually IAS as the forces exerted on the airframe are by IAS, the airplane doesn’t “know” true.

VNE is indicated, not true, you can safely exceed the true AS that equals NVE at altitude so long as you don’t exceed it in IAS. That’s for aircraft types like us that don’t have a MMO. 

MMO is I believe a critical Mach number, exceed it and Mach tuck is very likely, which may not be survivable as it’s an uncontrolled dive, as you have already exceeded a critical A/S last thing you need is an uncontrolled dive.

Now sometimes VNE on some helicopters could be because the upwind blade tip goes transonic at that speed and suffers Mach tuck, Maybe other aircraft’s VNE is transonic limit I don’t know, some I’m sure are?

Maybe even sometimes the barber pole comes first so there really isn’t a VNE, but just an MMO?

Speculation.

[A64Pilot]

15 hours ago, 47U said:

The air is extremely smooth up there.  I was on the U-2 mx side for the last half of my career.  The air was so smooth in fact, when Lockheed updated the U-2 avionics with a glass cockpit and digital autopilot (mid ‘90s timeframe), after a couple hours of stable flight, the rudder servo would randomly kick hard and then disconnect the axis.  Understandably, the pilots did NOT like that.  We submitted a formal request for ‘engineering assistance’ and after analyzing the issue, Lockheed updated the software and the problem disappeared.  

As to turbulence, there was an orbit off the Korean peninsula that, during a certain time of year, was known for its ‘wave,’ for lack of a better term.  It was so pronounced that new pilots on their first deployment were sometimes restricted from flying that mission.  One pilot got into a wave that ultimately  exceeded the aircraft’s roll rate to recover, so what does he do?  He takes it on around and rolls the airplane, at FL70+.   At the mission debrief the intel community, recording the telemetry of the azimuth on aft datalink antenna, verified that airplane executed an aileron roll.  

Pilot’s call sign… the “Wookie.”

Apologize for the thread drift…

I was stationed at Camp Humphries, the U-2’s would shoot as crazy as this sounds but I believe the ADF approach there and go missed. My God the thing could climb and was quite loud too, it was then that I learned that a U-2 was based on an F-104 with very different wings of course.

[Pinecone]

1 hour ago, Will.iam said:

Don’t know about 737 but a tanker which is basicalky a 707 will reach coffin corner as low as 40,000ft because you are so heavy with fuel you need to go so fast to offset the weight but you can’t as you are hitting against mmo. This wasn’t an issue with the old A model engibes as they lacked the power to lift that much weight that high but with the R model engines had way more thrust able to lift it but the wings can’t generate enough lift without going past mmo. I would think the 757 would be the sanme with it’s excess thrust capacity. 

I just picked the 737 and Googled for the numbers.

I am sure different aircraft have lower, it was just interesting that a Mooney and 737 have similar coffin corner altitudes. 

It was not a problem in the A-10, there was no way to hit MMO in that aircraft.  Even in a 60 degree dive bomb pass we did not get close to the barber pole.

[N201MKTurbo]

1 hour ago, Pinecone said:

I just picked the 737 and Googled for the numbers.

I am sure different aircraft have lower, it was just interesting that a Mooney and 737 have similar coffin corner altitudes. 

It was not a problem in the A-10, there was no way to hit MMO in that aircraft.  Even in a 60 degree dive bomb pass we did not get close to the barber pole.

I was driving to Rocky Point a while back and was driving just south of Gila Bend. The road goes through the Barry Goldwater range (restricted) There were two A-10 doing target practice on a target about 1/2 mile from the road. I pulled over to watch they were flying about a 1000 foot pattern till they got just about over the road, then they pitched down sharply. You could see the smoke from the guns and the dust kicking up from the target. They would pull up at about 200 feet.

Cool as hell! best air show I've seen in a long time.

[Pinecone]

I don't know.  I have never seen it.

Done it, but never got to see it.

 

[T. Peterson]

On 9/21/2022 at 4:23 PM, takair said:

Probably fair to share that Dave and I worked on getting his altitude hold tuned.  Great learning experience.   When I set up your dynertial on my plane I was using about 150mph and up….so it was definitely optimized for a higher speed.  This is likely why you have had to adjust the decay and may require additional adjustment if you typically fly at a lower speed. 

I think PT20J is correct about what is perceived as the “step”….it is really just getting to trim speed.  If leveling right at or below target, a Mooney takes quite some time….multiple minutes to get to trim speed.  The dynertial system can make it even more interesting since you need to anticipate its inputs too and the resultant trim might not be perfect every time.  Someone above mentioned climbing above target and settling to target, this can reduce getting to trim speed faster…by multiple minutes.  Another consideration is that when at a higher speed, one has more reserve energy.  So, at 120mph, if you get below target altitude, it can take more pitch or more time to get back on target altitude.  This might give that feeling of slower response as opposed to higher speeds where the reserve energy more rapidly gets you back on target altitude….basically trading airspeed for altitude.  If you have more airspeed, you can convert it to altitude faster.  The autopilot has similar constraints, but it has more limited knowledge and less things to help it come back to target.  For example, when hand flying, you may fine tune the trim and power, but the dynertial only has its limited authority on the elevator, so it will behave slightly differently….especially since set up for a higher target speed.

Very interesting. I am not smart enough to have an opinion, but I am certainly going to climb above and descend to cruise, then wait till I am quite certain I am beyond cruise speed before pulling back the power!!

It may be an OWT, but if there is a smidgeon of truth to it I am going to take advantage of it!

Thanks for sharing!

[A64Pilot]

6 hours ago, Pinecone said:

I just picked the 737 and Googled for the numbers.

I am sure different aircraft have lower, it was just interesting that a Mooney and 737 have similar coffin corner altitudes. 

It was not a problem in the A-10, there was no way to hit MMO in that aircraft.  Even in a 60 degree dive bomb pass we did not get close to the barber pole.

What Mooney has a coffin corner? I didn’t think any could get that high, our wing loading is so low that it would take way more altitude than we could get to.

Reason a U-2 has such an enormous wing is to push that altitude to ridiculous heights. Same for the Reece version of the Canberra 

727 was unusual in that it had more engine than wing, most Airliners run out of engine first I believe, by design, but the 27 was designed to climb out of Colorado and cross the Rockies on two I believe. So the pilots learned to cheat and pull the slats CB and sneak in 2 degrees of flap I think it was.

[Scottknoll]

What Mooney has a coffin corner? I didn’t think any could get that high, our wing loading is so low that it would take way more altitude than we could get to.
Reason a U-2 has such an enormous wing is to push that altitude to ridiculous heights. Same for the Reece version of the Canberra 
727 was unusual in that it had more engine than wing, most Airliners run out of engine first I believe, by design, but the 27 was designed to climb out of Colorado and cross the Rockies on two I believe. So the pilots learned to cheat and pull the slats CB and sneak in 2 degrees of flap I think it was.

I think you’re right about the 2° flaps. If true, and depending on who you believe, it almost killed an entire plane full of people:

https://en.wikipedia.org/wiki/TWA_Flight_841_(1979)

[Pinecone]

10 hours ago, A64Pilot said:

What Mooney has a coffin corner? I didn’t think any could get that high, our wing loading is so low that it would take way more altitude than we could get to.

Reason a U-2 has such an enormous wing is to push that altitude to ridiculous heights. Same for the Reece version of the Canberra 

727 was unusual in that it had more engine than wing, most Airliners run out of engine first I believe, by design, but the 27 was designed to climb out of Colorado and cross the Rockies on two I believe. So the pilots learned to cheat and pull the slats CB and sneak in 2 degrees of flap I think it was.

 

I said there is one, but you might not be able to reach it.

As I stated, the altitude for my 252 would be about 60,000 feet.