True.  I recall this being the centerpoint of another discussion about the 250/10 issue.  To be honest, I don't think I found anything 100% conclusive, but in a manner similar to case versus written law, it seems the vaguery is made clearer by how the regulatory bodies enforce it.  In the US, at least, it seems that the FAA interpretation is clean speeds.

Indeed, so far what I've found in terms of written sources say that the 250 below FL100 applies even if min clean is higher, however it seems that being unable to fly 250 knots clean may be one of the reasons ATC will lift hte speed restriction when that is requested.

True, but operating dirty is still operating safely

Not necessarily true. refer to FAA part 25 performance.

 

I stated above that you would not be able to validate climb performance with flaps or slats hanging. accel height is driven by certification regs. Procedures in the AOM are there for a reason, trust me or refer to part 25. Lets look at some info from my DC10 manual.

 

Climbing dirty is not an option unless you delay for necessity. I gave a few earlier.

 

There are no charts to compute climb gradients with flaps/slats hanging above accel height. At that point you become a test pilot.

min maneuver is you min safe speed.

 

If climbing dirty was the case, the manufacturer would have to give the flight tested recommended configuration and procedures. The climb schedule would say, if under the 250kts restrictions, fly with this configuration/fly this configuration without speed restrictions. they would also have to provide charts other than abnormal/emergency sections to prove that you can make climb restrictions. Flying around with flaps/slats hanging would kill your climb performance and max takeoff capability. Flaps/slats are great for getting off the ground, but they make very good drag devices. The last thing ATC wants is a heavy and configured aircraft churning out some vicious turbulence. Remember that a aircraft produces the most turbulence when it's heavy, configured and slow. It makes total sense to allow him to accel, cleanup and get on through your airspace. For this reason heavy is attached to your call sign as a constant reminder. He/she has to state heavy when they mention you.

 

The big point is to safely/quickly transition from dirty to a clean configuration engine out. This is why takeoff thrust is extended to 10 minutes with an engine loss. Having all engines operating is bonus as far as takeoff is concerned. The only difference between engine out and all engine is v2 plus 10 vs v2, takeoff thrust time limit extension, and a continued climb at accel height as you accel and clean up. You want to clean up to protect yourself from engine failure.

Not necessarily true. refer to FAA part 25 performance.

 

I stated above that you would not be able to validate climb performance with flaps or slats hanging. accel height is driven by certification regs. Procedures in the AOM are there for a reason, trust me or refer to part 25. Lets look at some info from my DC10 manual.

 

Climbing dirty is not an option unless you delay for necessity. I gave a few earlier.

 

There are no charts to compute climb gradients with flaps/slats hanging above accel height. At that point you become a test pilot.

min maneuver is you min safe speed.

Which is fair enough but then you would still have to request it from ATC, you can not ignore the speed restriction without prior permission. As mentioned above being unable to maintain less than 250 due to configuration is one of the reasons when ATC will lift the speed restriction in the london TMA.

Which is fair enough but then you would still have to request it from ATC, you can not ignore the speed restriction without prior permission.

 

...except in the US, as set by FAR 91.117d and reflected in 7110.65 5-7-2 Note.

 

This is reflected in practice.

 

Edit: I see you referred to the London TMA in the next sentence, but for the clarity of others...

Ok let's cut to the chase, has anyone ever heard a request to fly minimum clean speed? In over ten years I have never heard it. More so I have never spoken to any flight crew that have needed to do so.

 

One last thing, how is the bust enforced in the real world? You fly your clean speed which is 265kts indicated for example, unless ATC ask for a confirmation or data is pulled from the aircraft post flight they have know way of telling what your IAS is.

...except in the US, as set by FAR 91.117d and reflected in 7110.65 5-7-2 Note.

 

This is reflected in practice.

 

Edit: I see you referred to the London TMA in the next sentence, but for the clarity of others...

Yes my reference was for the UK, thanks for clarifying

 

 

Ok let's cut to the chase, has anyone ever heard a request to fly minimum clean speed? In over ten years I have never heard it. More so I have never spoken to any flight crew that have needed to do so.

 

One last thing, how is the bust enforced in the real world? You fly your clean speed which is 265kts indicated for example, unless ATC ask for a confirmation or data is pulled from the aircraft post flight they have know way of telling what your IAS is.

I have heard requests for min clean but it is usually in the approach world (instead of 220 knots some heavies prefer min clean).

 

Also the london TMA now requires mode S and the enhanced mode S that most airliners today are equipped with allow ATC to view the curent IAS from the cockpit. This is also used to monitor speed compliance on a daily basis.

I don't really want to throw a spanner in, but part of one of the statements was along the lines of "..the 250Kts speed limit is an essential part of the see and avoid action...."

 

Surely, on an instrument departure procedure the responsibility for separation lies with the controller and so see and avoid is not the primary method of applying separation? I'm not going to profess to know the score as I'm neither a professional aviator nor controller; but from the cockpit DVD's I've watched I've never seen a request for a speed greater than 250, but I have seen it offered by ATC - whether this is a SOP based on aircraft type then I'm not qualified to say.

 

 

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Yes on approach is a whole differant story. Anyway, I am on holiday in the Uk but have sent a quick email out to try and put this to bed once and for all. this is just one of those FS/Real world topics that keeps popping up and frustrates me to no end!

 

Hopefully I should get a reply that I can post here shortly.

 

@Tom, high speed departures get given or requested quite a lot, I've flown out heathrow many times on the jump seat and we are straight up to 340 knots ignoring the 6000ft DVR restriction, other times we just droned along at our clean speed along the SID until we are cleared higher.

I don't really want to throw a spanner in, but part of one of the statements was along the lines of "..the 250Kts speed limit is an essential part of the see and avoid action...."

 

Surely, on an instrument departure procedure the responsibility for separation lies with the controller and so see and avoid is not the primary method of applying separation? I'm not going to profess to know the score as I'm neither a professional aviator nor controller; but from the cockpit DVD's I've watched I've never seen a request for a speed greater than 250, but I have seen it offered by ATC - whether this is a SOP based on aircraft type then I'm not qualified to say.

 

 

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That is correct but most instrument procedures still have speed limitations. These are usually to reduce the differences between relative speeds and to make turn rates more predicatable for controllers.

 

 

Yes on approach is a whole differant story. Anyway, I am on holiday in the Uk but have sent a quick email out to try and put this to bed once and for all. this is just one of those FS/Real world topics that keeps popping up and frustrates me to no end!

 

Hopefully I should get a reply that I can post here shortly.

With you on the frustration bit! I've also dropped a line to a friend of mine who knows more about this so we'll see what he says.

Keep in mind that the same governing body that created the 250 below 10 are the exact same guys who approve the flight manual and it's procedures. The manufacturer goes to the governing aviation body to get those above 250kts climb schedules approved. In a sense, when they approve the climb schedule during type certification, they have acknowledged that the type requires speeds greater that 250 below 10. Otherwise, they would not approve the climb schedule. For example, a DC10 scraped it's tail after the co-pilot allowed the nose to exceed 10 degrees after touch down. The ground spoilers causes the nose to rise as they deploy. The FAA forced the manufacturer and operators to include the spoiler pitch up into the manual and training programs.

On a ending note, as far as 250 below 10, I've been above that speed thousands of times in 13 of flying DC10s. When ever there isn't any sid/turn/traffic restrictions, I exceeded it without asking. I've done it in the states and all over the world. I never exceeded when I was below the weights that required it. During sims/flight training, we have all ways exceeded it with out asking at those weights. The speed below 10 was one of my kc10 checkride questions I would ask new guys. In that community, we  were taught that codes and type listed on the flight plan lets ATC know. Since I have never been questioned about my speed, it leads me to believe that he/she knows by my flight plan or ATC could care less about this rule we are debating.

On another note, here are some pics from my flight last week.

Awesome CB picture Rick

Awesome CB picture Rick

Thanks, it was a lone soldier so grabbed a pic. It wasn't building fast or bubbling. The interesting weather came while departing UUWW. We departed just after mid night with light rain with a 600ft ceiling. When handed off to departure, tower said clear to turn left or right. Just as I looked at the co with confusion we hit moderate turb with the sound of heavy rain against the windscreen. Both radars painted nothing as we ran the tilt up and down. I increased the climb rate as we followed the sid. Flying blind sucks lol. I did have fun refreshing QFE ops. Some work trying to convert QFE to a QNH to add to the cabin pressure controller for landing. I guess I could have asked for a QNH but didn't want the Russians complaining about us wimpy Americans lol. We had enough difficulty trying to understand each other.

What  are the definitions of  "minimum safe airspeed for any particular operation" and "minimum manoeuver speed"?