View Full Version : Clb Gradient -all- Eng. Ops

12th Mar 2008, 14:09
Anybody knows,
( besides checking amber stars on the clb wpts of the FMGS for AI ),

how can we know if we are going to be able to comply with all the vert. restrictions in an ALL ENGINES OPS SID with a clb. grad. greater than the one needed with n-1 in a company built EOSID for the same RWY ?


12th Mar 2008, 14:57
As one who used to operate BAe146-200 in ISA+25 conditions, with nil FMS assistance, clearing altitude restrictions all engines operating was sometimes a challenge!

1. Why bother with ALL requirements?

Pick the most restrictive, eg, the one 'step' that requires the greatest gain in altitude in the shortest distance.

Provided your groundspeed does not vary greatly, if you clear the most restrictive, you are looking good to clear the others. Use the items below to see if/how you will clear the most restrictive.

2. Use Rule of Thumb: :ok:

Groundspeed x Gradient = Rate of Climb (or Descent) to make the Gradient.

E.g. 4.0% gradient required to 4200'. V2+10 climb target airspeed = 150kt. 150 x 4.0 = 600. You need to make 600fpm or better at that speed.

Or: 250KIAS climb. 3.3% gradient to FL080. Fudge in some TAS. Try 270 x 3.3 = 890fpm. If you are doing 1000fpm or better, you are laughing like fat spiders.

I don't know too many twin- or three-engined turbojets that couldn't make those gradients with all engines operating.:cool:

Don't know the Gradient? :confused:

Use ratio that you use for Wx RDR. 1 degree of tilt is approximately 100' at 1nm. Therefore two waypoints that are 12nm apart, the second with an alt requirement 3000' higher is a gradient of how many degrees ....

.... give it a try, you tell me! :)

3. Use 'the bird' if you have glass.

Note required gradient. In your Vertical Speed/Flight Path Angle window, toggle FPA on climb (without making an FPA selection) whilst doing the climb in another mode. In my aeroplane, the green target comes up on the PFD telling me the gradient it is making right now.:cool:

4. Pay attention when you DONT have a requirement.

On a nice day, at or near max TOW, put down your newspaper and note how many miles/DME/GPS/DTR your aeroplane needs to climb 1000' all the way to TOPC. :ooh:

Put it in your little notebook of factoids that you keep for a rainy day. Pull it out on the rainy day and refer.

e.g. a real stinker, the old BAe 146-200 at ISA+15 all ant-ice off..... 2.5nm per 1000' below FL100 at 250KIAS, 3nm per 1000' at 280KIAS to FL200, 4nm/1000' above FL200.

"I'm doing all that, and it is not making the gradient!"

1. Reduce to min clean speed (Vmin+5 or +10)
2. Set MCT (Max continuous thrust).

Much less forward speed with little or nil reduction in RoC = better ANGLE of climb. :ok:

15th Mar 2008, 03:59
Good evening.

Bestglidespeed, you might be interested in this thread.


Because most all-engines climb data provided to line pilots is not continuous from take-off through flap retraction, most of the time you cannot predict your actual compliance with a SID gradient.

This is a known problem. All engine climb profiles are not always steeper than the engine out versions, there is no certification requirement to produce all engine profiles (although manufacturers may produce some useful data as part of a community noise document for the FAA), and the forensic method of measuring actual climb performance takes place after you've already made the contract with ATC that you'd actually do it. Hard to explain when your aircraft is grossly underclimbing and can't safely make up the difference.

This won't change till the regulators force the data to be produced.



15th Mar 2008, 10:32
What the guys already explained is very helpfull. Thanks in deed. What I am doing in this case is that, As ITCZ said, multiplying groundspeed with required gradient and reaching rate of climb necessary to comply. If actual r/c is higher than calculated good to go. I mean no way to know it before you take off. If your r/c is lower than required You should inform the Atc and ask for revising your SID or radar vector. byee