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Old 21st Mar 2017, 14:52   #841 (permalink)
 
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Ah, but you've been well trained SAS
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Old 21st Mar 2017, 19:10   #842 (permalink)
 
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The RFM surely is a result of testing by manufacturer test-pilots?
If there was sufficient commercial pressure from operators saying they wanted to perform IMC hover takeoffs, then they would presumably test the helo under these conditions and approve a profile?
I can only assume that the profile is not there because there has not been the overt demand for it.
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Old 21st Mar 2017, 19:57   #843 (permalink)
 
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You know what happens when you "assume"!
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Old 21st Mar 2017, 20:15   #844 (permalink)
 
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I'm not going to get beaten with that hosepipe again?
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Old 21st Mar 2017, 21:46   #845 (permalink)
 
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Shy
Thanks for bringing this CAA Safety Notice up. Overall I must say I think it is a good effort from the CAA, particularly as it is for guidance. As you say too, important that they clearly accept private site IMC departures. Whilst I'm with Crab (and probably you) that 0/0 departures are not a problem given training and a good AFCS, the issues ref Vmini in the RFM are valid and achieving Vmini is a much easier departure technique. One thing I would say ref their criteria for establishing suitable AOM, is the loading of the acft, which was not mentioned. Ultimately it is all about acceleration, and there is a huge difference in a mid weight acft, which may achieve Vmini in 250m, and one at MTOW when well over twice that may be required, with a much lower climb gradient subsequently.
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Old 21st Mar 2017, 22:04   #846 (permalink)
 
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Non-PCPlod - the Vmini will be mainly due to the inacuracies of thec pitot.static system since very few give IAS below 40 or so kts with any reliability and some airspeed tapes dont have any figures below 30 kts.

Since that speed is required to fly the aircraft accurately (notwithstanding what a good AP is allowed to do using other sensors), it is no surprise that they don't test or certify it in the low speed instrument regime.

It's not that the aircraft can't do it because we all know they can but no-one is going to risk the litigation when someone spears one in flying in cloud at 30 kts by saying it is safe to do so.
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Old 21st Mar 2017, 22:17   #847 (permalink)
 
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Shy
Thanks for bringing this CAA Safety Notice up. Overall I must say I think it is a good effort from the CAA, particularly as it is for guidance. As you say too, important that they clearly accept private site IMC departures. Whilst I'm with Crab (and probably you) that 0/0 departures are not a problem given training and a good AFCS, the issues ref Vmini in the RFM are valid and achieving Vmini is a much easier departure technique. One thing I would say ref their criteria for establishing suitable AOM, is the loading of the acft, which was not mentioned. Ultimately it is all about acceleration, and there is a huge difference in a mid weight acft, which may achieve Vmini in 250m, and one at MTOW when well over twice that may be required, with a much lower climb gradient subsequently.
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Old 22nd Mar 2017, 08:54   #848 (permalink)
 
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rotorspeed, couldn't agree more. The Emmental lines up very quickly with 'it's in my tool bag' ... 'I was shown this once 3 years ago' .... instructors should be explaining this guidance to the pilot to allow him to challenge the customer, negotiate the payload deduction, point out lack of experience, refuse the flight - as they also say they have been brave enough to do, on their posts on this site.
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Old 22nd Mar 2017, 11:51   #849 (permalink)
 
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Crab-
If they certify the SAR modes so that you can do a TU from the hover, it has kind of been proven that it is both possible and safe (if you have this phase of the software). Therefore, the Vmini should not be an issue. It kind of seems pointless having a TU mode if you can't use it IMC - e.g. at night over the oggin.
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Old 22nd Mar 2017, 12:45   #850 (permalink)
 
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The SAR modes will use other sensors (GPS, accelerometers, inertial nav, even doppler) to give the speed which is why they are allowed to control TU/TD at low speed.

If the aircraft had a low speed display (LVI or groundspeed on the PFD/ND) then it could be used by the pilot for low speed IF but whether such 'extras' would be specified during the certification process I don't know.
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Old 22nd Mar 2017, 14:24   #851 (permalink)
 
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Quote:
Originally Posted by crab@SAAvn.co.uk View Post
The SAR modes will use other sensors (GPS, accelerometers, inertial nav, even doppler) to give the speed which is why they are allowed to control TU/TD at low speed.

If the aircraft had a low speed display (LVI or groundspeed on the PFD/ND) then it could be used by the pilot for low speed IF but whether such 'extras' would be specified during the certification process I don't know.
Exactly - which kind of makes the VMini a strange restriction if you have the other kit.
139s all display groundspeed, and provide a "hover display" as an HSI option, to show low speed vector (both direction and speed)
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Old 22nd Mar 2017, 14:59   #852 (permalink)
 
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Yes, perhaps it should be 'Vmini when hand flown' or similar - it's all a bit of a nonsense.
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Old 22nd Mar 2017, 16:06   #853 (permalink)
 
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Originally Posted by Non-PC Plod View Post
Exactly - which kind of makes the VMini a strange restriction if you have the other kit.
139s all display groundspeed, and provide a "hover display" as an HSI option, to show low speed vector (both direction and speed)
Hello Gents!

I am an average SARpilot (currently flying with AW139) and doing my best to follow your discussion. Just curious: how would You describe a SAFE 0/0 takeoff with coupled modes? Any suggestions?
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Old 22nd Mar 2017, 16:19   #854 (permalink)
 
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No knowledge of the 139, but I assume there is Force Trim, Heading Hold, Attitude Hold, and the ability to Trim the Attitude Datum while the Pilot can control power setting via the Collective position?

Last edited by SASless; 22nd Mar 2017 at 17:11.
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Old 22nd Mar 2017, 16:33   #855 (permalink)
 
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Quote:
Originally Posted by crab@SAAvn.co.uk View Post
Yes, perhaps it should be 'Vmini when hand flown' or similar - it's all a bit of a nonsense.
Sadly Crab the rules for certification are not that accommodating.
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Old 22nd Mar 2017, 17:20   #856 (permalink)
 
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Originally Posted by Search&Rescue View Post
Hello Gents!

I am an average SARpilot (currently flying with AW139) and doing my best to follow your discussion. Just curious: how would You describe a SAFE 0/0 takeoff with coupled modes? Any suggestions?
Come on Geoff, I know you can explain this
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Old 22nd Mar 2017, 18:10   #857 (permalink)
 
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Originally Posted by SASless View Post
No knowledge of the 139, but I assume there is Force Trim, Heading Hold, Attitude Hold, and the ability to Trim the Attitude Datum while the Pilot can control power setting via the Collective position?
I was just wondering if there is a procedure (published or not) which guarantees either safe landing or flyaway during 0/0 takeoff?
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Old 22nd Mar 2017, 18:16   #858 (permalink)
 
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Is there a guarantee for such for any takeoff if one includes all contingencies?

Aviation is based upon accepting reasonable risks is it not?

Consider the 225 situation extant!



Quote:
Originally Posted by Search&Rescue View Post
I was just wondering if there is a procedure (published or not) which guarantees either safe landing or flyaway during 0/0 takeoff?
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Old 22nd Mar 2017, 19:44   #859 (permalink)
 
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Originally Posted by SASless View Post
Is there a guarantee for such for any takeoff if one includes all contingencies?

Aviation is based upon accepting reasonable risks is it not?

Consider the 225 situation extant!
Thanks for your kind reminder! "Guarantees" was not an optimum word. Point taken And of course there are risks involved, even if you
are flying Cat A profiles... On the other hand the RFM describes e.g. how to use RHT/HOV and TU-modes...
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Old 22nd Mar 2017, 20:01   #860 (permalink)
 
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Search&Rescue,
How do you do it?
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