[jhb_airlines] Re: No speed restriction

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Wed, 21 Sep 2005 14:30:32 +0100

Speed restriction on most SID's is 250kts so I'd be interested if you have
found any that specify anything slower.

When I give a no speed restriction instruction to pilots I mean that you can
exceed the 250kt limit below FL100. Most jets these days use a 290/300kt
climb speed up to the point where it hits M0.76 and then fly a Mach climb
after so 250kts up to FL100 is a bit restricting.

If it helps here is a snippet from a Speed Control document I have:

"Looking at a typical climb/descent profile for an MD80 the following can be
observed.
The aircraft climbs at 290 knots IAS until it reaches Mach .76. It continues
the climb
maintaining .76 to cruise altitude, cruises at .76 and holds that Mach speed
in descent
until reaching 290 knots IAS again. As there is a speed limitation of 250
knots IAS
below FL100 the initial climb will be at 250 knots IAS (289 Kt TAS/Mach
.45). The
aircraft will then accelerate to 290 knots IAS (334 Kt TAS/Mach .52 at
10,000 feet) and
then climb at this constant indicated speed.

During this climb both the TAS and Mach number will be increasing as
follows:

                TAS             Mach
15,000  359kt   .57
20,000  387kt   .63
25,000  418kt   .69
29,000  445kt   .75**
33,000  441kt   .76 (268 kt IAS)
37,000  435kt   .76 (245 kt IAS)
** From this point on the pilot will fly at Mach .76 and no longer use IAS
as a
reference unless requested to do so by ATC.

If the crew had not changed from IAS to Mach number and tried to hold 290
knots
IAS all the way to FL370, the speed at top of climb would be Mach .88 ? far
in excess
of the permitted limit.

In the descent the process is reversed. The pilot will fly at Mach .76 until
the IAS
reaches 290 knots, which should occur around FL290. During this part of the
descent
the aircraft will accelerate slightly from 245 to 290 knots IAS (435 to 445
Kt TAS). In
the descent from FL290 to FL100 the aircraft will be flown at a constant 290
knots
IAS and the TAS will decrease from 445 to 334 knots. IAS will then be
reduced to
around 210 knots in preparation for configuring the aircraft for approach.

bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Phil Reynolds
Sent: 21 September 2005 12:35
To: JHB
Subject: [jhb_airlines] No speed restriction


Hi Bones,

Another ATC query.  In my last online session I departed on a specific SID
with an initial altitude of 4000ft given. Once contacting the APP controller
he advised to climb to FL120, no speed restiction.  Does the no speed
restiction just overrule any SID speed restictions or does this instruction
also overrule the 250kts below 10000ft (in the UK) rule?

Cheers

Phil




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