Need help with this chart

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Need help with this chart

Postby Irfan Ahmed » Sun May 29, 2022 11:55 pm

Hi guys,

I want to fly the return leg from Liverpool to Jersey on the BAe 146-100 using radio navigation only. However I want to attempt to fly a SID out of Liverpool (EGGP) that is based on VORs. Don't know whether that would be possible but I do want to give it a shot.

I want to use the SID NANTI. Now, it says "Climb straight ahead. At I-LVR D1 or 580 QNH (500 QFE) if sooner, turn right to WHI NDB, crossing WHI NDB at 3500 ........" I'm not a real pilot so I don't understand how will I know that I've climbed to 580 QNH or 500 QFE?

At another point in the chart (sorry, I could not upload a screenshot of the chart. I did upload it on google and pasted the URL here but it was tiny and hardly viewable) it says "RWY 27. Aircraft of more than 5730KG (12500LB) climb straight ahead at maximum rate to 1081 QNH (1000 QFE)" I understand climbing to feet or meters but never used QNH to climb to a certain altitude.

Any help would be appreciated. I got the charts from Chartfox.org.
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Re: Need help with this chart

Postby chopper_nut » Mon May 30, 2022 8:19 am

QNH is setting the altimeter relative to sea level pressure.. QFE is something they seem to love in the UK more than anywhere else and reads your height above the threshold (altimeter will read zero on the runway) the chart is just giving you instructions for both depending on what your altimeter is set to.
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Re: Need help with this chart

Postby deeknow » Mon May 30, 2022 8:44 am

Interesting re the QNH/QFE references, thanks CN :thumbup: Our NZ plates tend to just quote stuff like "Maintain RWY CL to 500ft" for early turns don't they. I guess that assumes you have your QNH set correctly

Irfan, I guess you must have a VATSIM account if you are using ChartFox, you could consider posting in the VatUK forums for questions about their procedures?
https://community.vatsim.uk/
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Re: Need help with this chart

Postby chopper_nut » Mon May 30, 2022 9:07 am

Yeah, NZ, AU, US, CA all tend to just use QNH. I've only heard of QFE in England but yeah maybe ask the UK specific crowds
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Re: Need help with this chart

Postby Lindstrim » Mon May 30, 2022 9:38 am

Having a look at the chart you'll need to climb at max rate till the altimeter read 1081ft when using the local QNH. (eg a QNH of 1013 is equal to 29.91 in) Don't worry about QFE it's pointless in this exercise.
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Re: Need help with this chart

Postby Irfan Ahmed » Mon May 30, 2022 10:49 am

Lindstrim wrote:Having a look at the chart you'll need to climb at max rate till the altimeter read 1081ft when using the local QNH. (eg a QNH of 1013 is equal to 29.91 in) Don't worry about QFE it's pointless in this exercise.


Really? I didn't know it was that simple. I do know QNH when it comes to setting the altimeter but never heard anyone say "climb to XXXX QNH". Thank you!
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Re: Need help with this chart

Postby chopper_nut » Mon May 30, 2022 11:17 am

Again, you hear it in the UK
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Re: Need help with this chart

Postby Irfan Ahmed » Mon May 30, 2022 12:51 pm

chopper_nut wrote:Again, you hear it in the UK


LOL :lol:
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Re: Need help with this chart

Postby cowpatz » Tue May 31, 2022 11:13 am

Interestingly the QFE remark does not appear on the Jeppensen charts for this SID. What it does do is give a better appreciation as to how high above ground you will be which is useful when operating from an airfield that is well above sea level. Not that you should not set this QFE on the altimeter, just take note of the charted QFE heights.
A standard ICAO SID gradient is 3.3% and is easily complied with under normal operations.

How to determine if you can meet a different (other than 3.3%)specified gradient is not quite so easy.
There are 2 simple rules of thumb that can help.

To get the required rate of climb
Multiply your groundspeed by the gradient. ie a gradient of 5% at a GS of 150kts = 5 x 150 = 750 ft/min

To get the required feet climbed per nautical mile required
Multiply the gradient by 60 ie. a gradient of 5% = 5 x 60 = 300ft per nautical mile.

Usually the SID gradient rate of climb required is published in a table on the chart but the above rules of thumb can be used and are close enough.
The rate of climb is average and you need to take this into account during things like accelerating during flap retraction. For a standard SID reaching 2000ft (height above departure point) by 10nm is a good figure to remember. It is easier to set distance/altitude targets to meet rather than try and constantly monitor vertical speed. ie 5 nm at 1000ft etc
The other consideration is what to do in a multi eng aircraft in the case of an engine failure on departure. In a single engine aircraft an engine failure is relatively simple as there is only one way your gradient is going so just recite the Lords prayer and hope for the best. Just what to do in a multi engine aircraft in the case of an engine is best considered when on the ground prior to takeoff. Can I continue on the SID? How long will I remain visual for on departure and could I visually recircuit to land or maintain my own terrain clearance visually out towards lower terrain. In the case of airlines, they have performance engineers that calculate all of this for them. If the aircraft is unable to meet the single engine requirements of the SID then there will be a published engine out procedure to follow. As an example for our 787's departing San Francisco on runway 28L the TO performance calculation in the EFB will have a note that states: At 2.0 SFO turn right to track 305M.
So should an engine fail before 2 DME SFO then continue to that point then turn right and track 305 (not heading) and climb on that track to a safe altitude. If the engine fails after 2 miles then continue via the SID.

Probably more than you wanted to know but it is one of the more tricky, yet critical, aspects of instrument departures.
Last edited by cowpatz on Tue May 31, 2022 3:03 pm, edited 1 time in total.
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Re: Need help with this chart

Postby chopper_nut » Tue May 31, 2022 11:33 am

Can I enroll in your IFR ground school?
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Re: Need help with this chart

Postby Irfan Ahmed » Wed Jun 01, 2022 3:43 am

Thanks cowpatz
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