A welcome surprise Etudiant - I am far more used to abuse on this thread:ok:

Crab is very knowledgeable but be fair, you can be blunt to the point of insult on here, hence a least some of the ‘abuse’.

Also, re: BS, the MAUM of the S-92 you posted is incorrect 😁

Don't fly it, don't have an RFM so blame the internet - perhaps 26,500 lbs is correct - the figures were after all just for illustration about disc loading and downwash.

One man's blunt is another man's truthful - all depends where you are standing - I have apologised in the past when I have actually insulted someone:)

Fair enough Crab, no problem with blunt if it’s truth. It’s the more subjective stuff that I’ve protested (such as your comments on civilian SAR pilots). Yes, 26,500lbs for S-92.

Aren't they all civilian SAR pilots now? Much of my criticism at the time was slightly misdirected due to more organisational ethos concerns. I'm sure there are still good and bad in the Bristow setup.

AW189 MAUM is Incorrect also. 8.6T

Again, blame t'internet :ok: Even the Leonardo website says 8.3 or 8.6T - 8.3T is as close as to 18,300 lbs as make little difference

Throw the man a bone. 8.3T is certification, 8.6t is supplemental

LZ

The high downwash in the hover is explained by dividing the rotor disc swept area by the AUM of the aircraft to give disc loading in lbs/sqft

For the previous examples, 189 and 92 come out at just over 10 lbs/sq ft compared to the Sea King at 7 lbs/sq ft.

The downwash of the Sea King could be problematic in light winds so it is no wonder the newer helos have issues.

Back to the Wessex for coastal and inland SAR:) 56 ft rotor, 13,600 bs MTOW, 5.5 lbs/ sq ft disc loading :ok:

ok fair one

And the 139 comes out the best - 15000 lbs (approx without supplemental increase to 7000Kg), disc 54' 8" - disc loading 6.37 lbs/sq ft.

It certainly seems clear from a downwash point of view that the 139 is the best option from the Leonardo stable for coastal SAR - oh wait, isn't that what was used when the 189s weren't available?

I like the 169 from a size perspective but it comes in at 9.5 lbs/sq ft - however, being less than 2/3 of the mass of the 189 it would have far less downdraught.

What’s your calculations for the 175 Crab?

Using rotor diameter 48' 7", MTOW of 16,535 lbs the disc area is 1850 sq ft and the disc loading 8.9 lbs/sq ft

Not the entire story I suspect since the different blade tip and root designs along with the effect of the fuselage shape will have an effect on the working area under the aircraft. This subject was raised at the ICAR Air Commission a few years ago. Some makers had mapped the downwash under certain aircraft but I don't think we got any further with it since the science had never been done for most types. I am happy to work under the intense downwash of the new types since it is the same power that is keeping me safe in the air.

Most of the tip design is to improve forward speed - hence the much higher Vne and cruise speed of the modern aircraft compared to Sea King etc. The Carson blades would have given another 25 kts of speed to the Sea King without changing the downwash.

You can have the extra power to give great OEI performance for safety without the horrendous downwash, you just make the rotors longer but that isn't the fashion amongst designers who like to make the overall aircraft more compact (shorter tailboom for example) to increase the useful space in the cabin.

You don't work much in the water under the aircraft I am guessing Jim?:)

Second episode tonight, all mountain work, and every other word seemed to be downdraught. Modern helicopter design isn't focussed on what SAR needs.

Although we sometime feel like the hills of Wester Ross are as wet as the nearby ocean, generally, that would be a no! :cool:

Where downwash is a problem for us is on steep ground, narrow ridges, and avalanche-prone terrain. One can train MRT to deal with working under heavy downwash but the problem remains of persons in distress, and other members of the public, who have no comprehension of the forces involved.

So, given that the purpose of a SAR helicopter is to rescue people from difficult and dangerous situations - will we see a different choice of aircraft for the next contract or will it be more of the same?

Will any manufacturer actually design a SAR-specific helicopter rather than sticking a winch on the side of their offshore model?

No. The potential helicopter market is limited enough as it is. Why would they want to limit it further?

There are ambitions in some quarters to turn some parts of this service into something like Choucas 74 or Dragon 76. While I admire the work under those c/s, I also believe those admirable approaches would have a limited applicability in this territory and there would be no appetite for their number of bases.

EASA Mountain HEMS? Non, merci.

Within the scope of the current spec one could see H215. H175? 525? ??? What else?

Smaller, faster? Faster: no such thing. Eh ... AW139? Well, fine until the day you are 150nm offshore with IMC at your destination and no space to do proper work on your casualty.


The money is in making stuff for landing on runways and steel decks or as a weapons platform. I suspect an SAR market divides up into 3 or 4 territorial sectors with different size and performance requirements. Nobody will service that kind of marketplace with dedicated types.

The 139 is easily big enough to cope with that regardless but that would be a job in the very small percentage that occur more than 100Nm from base according to MCA stats so what is your point?

As I have suggested, a couple of longer range bases with big helicopters for those rare jobs and smaller, more user-friendly (from a winchman and casualty perspective) for everything else.

We don't have to go down the mountain HEMS route - I still think winching is far better than long-lining - and you need to be able to move MRT around but a 139 sized helicopter with lower downwash has to be a better option for coastal and mountain work.

I know a manufacturer won't design a whole new helicopter for SAR but offering an option with a longer tail boom to accommodate a larger rotor and thus reduce the downwash wouldn't be that difficult, would it?

Doing the latter is basically doing the former!

Not really - if all you do is lengthen the tail and put longer blades on it, the remaining systems (ie most of the helicopter) wouldn't need re-certifying. Not so different from putting a 5-blade rotor on a previous 4 blade type.

Bloody hell Crab. You should get yourself into no. 10. Talk about reversing your decisions! Have you had a bang to the head recently? Have you got to like the 139 now during the last 3 years or so?

I've been flying it for the last 2 years so yes, I do like it - it's not perfect and I know Bristow had some issues with it but for coastal and mountain work it is the right size helicopter with a manageable downwash.

Just trying to offer suggestions since the new contract process has started - chances are it will be more of the same with poor working conditions under the aircraft for the underpaid winchman again

There you go folks, miracles do happen. Crab has publicly said he thinks the 139 is good for SAR or at least two of the biggest aspects of it.

Bristow did have issues primarily related to the fips system which prevents the mast weight being installed to aid with reducing the vibrations. I think the lips system is better and sufficient.

But of course it isn't being used in UKSAR now and wouldn't have been if the contract had gone according to plan.

I don't like the nose up attitude in the hover but the power and the automation are good.

I hate the FMS which would be at home in an airliner but is not optimised for helicopter ops and I know Bristow had issues with the gyros for the AP due to vibration issues.

It is the size and downwash compared to the other modern types that makes it good - it's not a Wessex but you can't have everything

You could light a fag under a Whirlwind.

Especially usefull when searching for a fuel leak

A new source of business for SAR and MRT or a bright idea?


Great North Air Ambulance is trialling Jetsuits for their paramedics to reach those in need in hard to reach areas. Not sure what the casualty recovery plan is though?

Yep, jetsuits and drones - who needs helicopters?:)

They need to fly two in formation, or even four, to carry the stretcher.

... I hate to think where they would put the handles.....

Contract extension confirmed:

Bristow to continue delivering UK SAR helicopter service for HM Coastguard under extended contract | Bristow Group

During October, the Coasties signed off a document called Single Statement of User Needs (SSUN) that defines their requirements and at the end of that month they sent it out to Government Departments and Category 1 Responders for feedback. Feedback was due back by the end of November. Cat1 were asked to collate feedback from their SAR volunteers. The following video refers.
The SSUN is similar in many respects to the Technical Requirement Matrix issued in February 2012 as part of the previous contract process (and largely inherited from SARH25) that became Schedule 2.1 Specification of the current contract.

Much has been made of the Government policy for a service-based contract that concentrates on outcomes and does not prescribe methodology. There is something to be said for this approach since it may provide for greater bidder innovation. The SSUN layout and style reflect this approach.

However, it seems to me that the operator needs the customer to specify certain aviation requirements so that they have a clearly defined reason to write an appropriate safe procedure into their operating manual, which is key to approval by the regulator, who expresses that approval through the granting of an Air Operating Certificate. Do correct me if I'm wrong.