Clean speed above 250 kias

[Johnny Tightlips]

Hi all

This one is for the heavy driver's amongst us. Is there any heavy aircraft that has it's minimum clean speed above 250 kias and if so are they exempt from the 250 below ten restriction that is required on some SID's?

Thanks in advance.

[ghw78]

The 747 and 777 at heavy weights most certainly have min clean speeds above 250 kts.

Most countries permit you to fly at greater than 250 kts below 10000ft if this is the case but there is a requirement to notify ATC that you will be doing that.

The wording required varies between countries.

Not able to supply actual figures at present but willl give you some later.

[FE Hoppy]

yes and mostly yes if you ask.

[TopBunk]

The B747-400 at MTOW of 397 tonnes has a min clean speed of about 280kts

[Old Smokey]

The B777-300ER at MTOW has a minimum clean speed between 270-280 KIAS. ATC will typically approve a speed above 250 KIAS for heavy weight Takeoffs.

If ATC don't agree (I've never encountered it) the only option would be to leave Flaps at 1 (Slats) until 10,000 feet, OK under normal circumstances, but absolutely unacceptable in Icing conditions

Best Regards,

Old Smokey

[Johnny Tightlips]

Intresting answers. Thanks.

[kenparry]

B767-300 is also slightly above 250kt minimum clean at max TOM, but not by as much as those quoted above - around 254kt, IIRC.

[CP32]

All the destinations we go to in the 747-400 are so used to our clean speed on departure that we don't even bother to get clearance. Same applies to any "heavy" at any airfield that is used to them.

[ajd1]

Very close Ken; it's 258kts at 186880 kgs. I'm led to believe that exceeding the F5 speed limit of 240kts is still a common event on Hajj flights!!

[Wizofoz]

B767-300 is also slightly above 250kt minimum clean at max TOM, but not by as much as those quoted above - around 254kt, IIRC.

Yes but he specified the ER, Ken.

Got the QRH in front of me, 264kts at 350 000KG.

[Old Smokey]

Hey Wizofoz,

I think that Boeing may have great interest in you giving them a call, how to get 350,000 Kg from a B767-300ER

Now, if you,re talking B777-300ER, you're on the money

Regards,

Old Smokey

[Jetjock330]

Just completing 12th year on the A340 and I have never been asked to stick to 250 kts below 10000ft. We inform Departure "we require 275kts best climb", and have never been denied. A340-600 Increased growth we fly at weight 380 tons has minimum clean 273-275kts. After 10000, we go to 320 on all occasions to 29000ft (there about and then M.82/.83). Max is about 31000ft at that weight dependent on temperature outside.

Minimum clean, (green dot) is a function of weight and altitude. The formula was in the FCOM a few years ago and has since been removed, but it involves the weight at the current time and altitude. The formula also incuded an increase in green dot of approximately 1kt per thousand feet above 20000ft. This is to say that green dot increases with altitude to a point, however, above 10000 ft, we are at 320 kts and hence further away from minimum clean.

[aterpster]

Here are the FAA rules for the U.S. and territories:

§ 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 mph).

(b) Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.

(c) No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport or in a VFR corridor designated through such a Class B airspace area, at an indicated airspeed of more than 200 knots (230 mph).

(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.

(d) is the operative requirement for the OP's question.

If ATC has assigned a speed or there is a speed on the SID then the pilot must notify them is he/she plans to exceed 250 or any charted lower speed.

[Wizofoz]

Hey Wizofoz,

I think that Boeing may have great interest in you giving them a call, how to get 350,000 Kg from a B767-300ER

Now, if you,re talking B777-300ER, you're on the money

Regards,

Old Smokey

oops!!