# Is there an issue with an acceleration followed by a deceleration when flying a SID?

Sometimes I see SIDs with a long straight climb segment (say 10 nm), followed by a wide turn with an IAS constraint (e.g. MAX 210 KIAS).

Is there any issue in accelerating to 250 KIAS and then decelerating shortly before the turn? Is that ever done?

EDIT
Fictitious example:

EDIT #2
Here's the actual chart (I hope no copyright infringement):

• Can you provide an example so we can look at the plate? Thanks.
– user14897
Sep 10, 2018 at 15:22
• I'm referring to LIPY, but I'm not able to find a link w/o a registration (I fear that I cannot post the chart). I add another chart in my post with an example. Sep 10, 2018 at 16:34

In theory it is allowed (see nulla poena sine lege), but no reasonable pilot would do so.

The purpose of the IAS limitation on the turn is to limit the radius to keep aircraft within protected airspace. There is no such issue on a tangent segment.

However, it is a waste of fuel to speed up and then slow down within a few miles, and at best that will save you a few seconds of flight time. At worst, it creates a risk that you won’t slow back down in time for the curve, which could get you killed.

So, pilots will fly the first tangent segment at or below 210kt, and then accelerate once established on the second tangent segment.

The usual chart verbiage is, “do not exceed 210 KIAS until passing FIXXX”. That precludes speeding up and then slowing down.

While doing that & then slowing for the turn would probably maintain obstacle clearance (by keeping the turn radius to an expected value), you might compress with traffic ahead that is flying the expected profile. Also, some departures direct the slower speed to keep you climbing and minimize the noise impact to houses along the departure route.

• Please, take a look at the EDIT #2 for the actual speed restriction. Sep 10, 2018 at 18:48
• @Cristiano The distance shown in your example isn't enough for much of anything without an afterburner to climb to about 3,000' AND accelerate to 250 knots and then to slow back to 210. An F-15 probably could... but, why? In normal operations, what you suggest isn't done, at least in any departure I've ever seen.
– Ralph J
Sep 11, 2018 at 6:59
• If there is a problem with compression with a previous departure, the controller should issue a control action to keep the required longitudinal separation. Mar 28, 2022 at 12:21