No speed restriction climb

[Pastalucci 0]

Hello comunity, I have a question.

If for example, the ATC gives clearance of no speed restriction below FL100, what is the optimum climb speed? If in normal conditions I would accelerate above 250KT after passing FL100, if I receive this "free speed" let's say at 3000ft, should I accelerate to climb speed even at this lower altitude?

I am curious not about speed, because it seems that it would be a faster trip if accelerating below FL100, but regarding efficiency.

 

Thank you. 

[skelsey 765]

The FMC calculated ECON climb speed (ie whatever it would give you above FL100) will always be the most efficient speed for the weight and conditions. So essentially all you need to do is delete the 250/10000 restriction from the VNAV CLB page and let the FMC do the rest!

[Pastalucci 0]

8 minutes ago, skelsey said:

The FMC calculated ECON climb speed (ie whatever it would give you above FL100) will always be the most efficient speed for the weight and conditions. So essentially all you need to do is delete the 250/10000 restriction from the VNAV CLB page and let the FMC do the rest!

Thank you for the information. I thought it was like this, but I was not sure that ECON climb speed is also efficient below FL100 🙂. You said efficient for conditions; I always use simbrief, and in PERF page for the average wind and isa dev I put what simbrief gives in the summary: this being the average wind for the whole trip and isa dev. I saw somewhere that in order for the FMC to give the best climb performance, the average wind component and ISA should be the ones from TOC from the flight plan. 

What versions should fit best? Thank you.

 

[Pastalucci 0]

Coming back on this thread, what I found is that in the perf init page should be put the TOC winds and ISA DEV, in order for the FMC to calculate the best climb performance. When reaching cruise, the winds can be changed with the average wind components, in order to get a better estimation of fuel burn and time to arrival. If one wants so, the cruising waypoints can also be updated with each's forecast wind data from the flight plan, for better prediction. It seems that on shorter flights this is not so significant, but on a longer flight, where winds change, the climb wind and cruise wind can be totally different. This seems to affect the climb performance.

If someone with real-life or better sim experience can confirm this, I would be grateful.

 

Thank you.

[Spin737 102]

You're really starting to split hairs. High speed climbs can be more efficient. Should you do that at CLB or CLB-1 or CLB-2? CLB-2 reduces engine wear, but increases fuel cost.

Related anecdote: I flew in Korea for a bit.  A local captain was so sure that hi-speed climbs were saving his company a ton of money and that American ATC should allow it, too. I didn't tell him that any money he saved on the climb was eaten by only performing full approaches everywhere instead of a nice, short visual approach.

[Stearmandriver 2,266]

4 hours ago, Spin737 said:

.  A local captain was so sure that hi-speed climbs were saving his company a ton of money and that American ATC should allow it, too. I didn't tell him that any money he saved on the climb was eaten by only performing full approaches everywhere instead of a nice, short visual approach.

I remember another Asian carrier's attempt at a visual approach in San Francisco a while back.  I wouldn't have argued either ;).

On topic, the efficiency issue has to be about negligible.  Given the high density of VFR general aviation traffic that's not talking to anyone around many cities these days, I'm happier to not go any faster then 250kts and take the improved climb rate to get me above the fray quicker! 

[BlueStar 323]

F.A.R. 91.117 Aircraft speed.

"(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.)."

ATC can not approve speeds greater than 250 KIAS below 10,000 MSL in the US. 

Grace and Peace, 

[Stearmandriver 2,266]

Except... when they can.  😉 Houston had a test program for a couple years where they could approve a speed-restriction waived climb.  I couldn't do it in the jet I was flying at the time because of a limitation for bird strike protection, but the Boeings did it regularly.  I think a couple other cities had that test program too.

That was years ago though, and the rule didn't change.  I'm personally good with that; I fly GA also and would rather not mix it up with 320kt traffic. 

It is common elsewhere in the world though. 

[Captain Kevin 586]

1 hour ago, Bluestar said:

F.A.R. 91.117 Aircraft speed.

"(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.)."

ATC can not approve speeds greater than 250 KIAS below 10,000 MSL in the US. 

"(d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed."

I think a heavy jet with a minimum clean speed higher than 250 is able to fly at that speed rather than have to climb to 10,000 with the flaps out.

[BlueStar 323]

58 minutes ago, Captain Kevin said:

"(d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed."

I think a heavy jet with a minimum clean speed higher than 250 is able to fly at that speed rather than have to climb to 10,000 with the flaps out.

Kevin,

Part (d) above does not give the controller the authority to assign or approve a speed above 250 KIAS.

Grace and Peace,    

[BlueStar 323]

1 hour ago, Stearmandriver said:

Houston had a test program for a couple years

SWA sure seemed to like it. 🙂

Grace and Peace, 

[scandinavian13 5,192]

Just to add clarity:

117a - Note the lead in: "unless otherwise authorized [...]."
...and...
117d - Note the reference to "[...] the aircraft may be operated [...]."

117a references the fact that operator-specific exemptions exist. These are negotiated with the administration, and are incorporated into the approved Op Spec, which essentially becomes the FARs for that operator (and are enforceable as such). 117d references the fact that aircraft-specific exemptions exist. These are based, as the reg states, on the minimum safe airspeed, though no clarification is provided elsewhere in the FARs, AIM, or other handbooks.

None of the points in 117 provide an allowance for a controller to specifically approve any airspeed outside of the regs. The 7110.65 does, however, make a note that pilots will operate their aircraft in accordance with the parts of 91.117 without notification.

This brings about a few important points: Aviation is not as black and white as people make it out to be. The administration is not as clear as people assume it to be (and if you ask one FSDO, they may have a different interpretation than another FSDO, even if only slight). Grey areas are actually great in the fact that they provide room for discretionary operation. Nobody is going to authorize operation in the grey areas - controllers, specifically - so know your responsibilities and operate accordingly. To further this point, 14 CFR 91.3b provides the pilot exemption from the regs to properly address an emergency. If a pilot were to ask permission (incorrectly) from the controller to operate at 300+ knots below 10,000 to try and rush a passenger to emergency care on the ground, the controller will most likely (properly) deflect the question with a reference to operating the aircraft at the pilot's discretion.

Note: I am not a lawyer, and this is not legal advice. If you are operating an aircraft out in the wild, and have question on the regs, seek proper legal aid.

[Spin737 102]

19 hours ago, Bluestar said:

F.A.R. 91.117 Aircraft speed.

"(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.)."

ATC can not approve speeds greater than 250 KIAS below 10,000 MSL in the US. 

Grace and Peace, 

Other countries don't necessarily mirror US regs.

I've done +300 below 10k due to emergencies - Captain's Emergency Authority trumps 91.117.

[Pastalucci 0]

Regarding 250KT+ below FL100, I see there are heated arguments. In US it seems to be very rare occasions to break this speed limit, but in Europe is commonly seen. When I started this thread regarding the climb performance, I was listening to LiveATC, LROP (Bucharest Henri Coanda) TWR/APP. When there is not a lot of traffic, for departing aircraft, is commonly heard "proceed direct to <WAYPOINT>, free speed (or no speed restrictions)". Sometime this instructions are given even as low as 3000ft, probably after passing the noise abatement limit. 

 

Also very often I hear this instruction for descending planes, on approach. Only when they get close to the airport, and again, the traffic is not bad, they maybe get an "160 until 5". But usually high speed approaches are common around here. 

 

 

[skelsey 765]

4 minutes ago, Pastalucci said:

Regarding 250KT+ below FL100, I see there are heated arguments. In US it seems to be very rare occasions to break this speed limit, but in Europe is commonly seen.

This is because (as you will have seen above) there are regional differences!

In the US 250kt below 10,000ft is written in to law (with some exceptions as documented above). So ATC does not have the authority to authorise a higher speed, in the same way that, for instance, a police officer doesn't have the authority to permit you to break the speed limit (they may turn a blind eye, but if you got caught on a speed camera 'the policeman told me it was OK' wouldn't wash - they're not in a position to decide on who's required to follow the law or make up new laws on the spot).

In Europe and pretty much the rest of the world, 250kt below 10,000ft is mostly an air traffic control restriction (i.e. has no formal legal basis). As it is a restriction imposed by ATC, ATC in turn may elect to lift the restriction (in exactly the same way as they may lift an altitude restriction on a SID, for instance).

Whether or not is a good idea to go blatting around at 300+ kt at low level is another question (note that the usual form of wording is 'no ATC speed restriction' -- which is not the same thing as 'Fly 350 kts') and Andrew above has given one reason why one might consider keeping the speed down. Obviously the environment you are operating in is going to have a bearing (traffic situation, airspace class, airline SOPs, workload etc etc)... 'airmanship' is the watchword.