Ec135t2 sas mode - flight characteristics

[DOUBLE BOGEY]

Hi everyone,

I am interested in the flight characteristics of the EC135T2 when it is fitted only with SAS Mode. Does anyone have any flight experience of how stable the aircraft is in this mode. I understand the technical differences between ATT and SAS so I am not looking for a technical explanation.

I am specifically interested in the potential for an EC135T2 being flown on longish sea treks from islands to islands with SAS Mode engaged. Is it demanding/high work load?

How long can hands and feet be off the controls before the attitude departs dramatically.

The safety of such a proposition.

It would have a RADALT fitted.

Thanking all EC135 Pilots out there for the advice and guidance in this respect.

DB

[[email protected]]

The rad alt will need audio/visual warning since you won't have a rad-alt hold with just SAS.

I would suggest that if the workload is that high over the water (day or night?) then a 4 axis AP would be preferable.

Is it searching or perhaps survey work?

[DOUBLE BOGEY]

Hi CRAB - no its just positioning, one island to another. It will only have SAS with no ATT so no holds of any kind. Have you flown the EC135?

[MightyGem]

The rad alt will need audio/visual warning since you won't have a rad-alt hold with just SAS.
Do they have Rad-alt holds? Ours only had Bar-alt hold.

[Sir Niall Dementia]

Do they have Rad-alt holds? Ours only had Bar-alt hold.
MightyGem;

I've flown half a dozen different ones and they've only ever had baralt hold.

If the latest (T3) version has radalt hold I don't know.

SND

[[email protected]]

DB - only in the sim a couple of times.

If the baralt hold is 'tight' enough it might be good enough for over water work hands off but a rad alt low height warning of some kind is essential for over water work in poor conditions or at night.

[FloaterNorthWest]

SND,

T3H has Rad Alt hold.

FNW

[DOUBLE BOGEY]

Hi CRAB an dFNW thanks for your input. However I really want to hear from pilots who have flown the 135 in SAS mode. Anybody out there with this experience I would really like to hear their opinions.

[Flying Bull]

Hi DOUBLE BOGEY,

only 135 experience in the sim, but real time on Bo105 (without SAS or ATT), BK 117 with SAS and ATT and EC155

The Bo 105 could be actually flown with weight shifting, if it was propperly trimmed out.

With SAS you will have the possibility to trim the bird - and if not disturbed, it will fly nicely straight and level - to give you the time to switch radios, punch in the GPS-waypoints and so on.
Evenso over water 3 or 4 AXIS AP is nicer to have, the workload won´t be excessive on a normal day.
Things will be different, if fog comes into the game or i.e. on the North See one of these grey days, where there is no horizon, the water having the same grey the sky has....

[skadi]

The 135 with SAS is ok, reduces the workload in comparision to the 105 . But for flights over open water I would prefer ATT, 4 axis AP with RadAltHold would be the optimum.
In smooth weatherconditions SAS is sufficient, but workload increases when it gets bumpy...
Most of my time (~2900h ) on 135 was SAS only... My offshore experience was with 3 or 4 axis AP equipped machines of different type

skadi

[DOUBLE BOGEY]

Hi SKADI thanks for the guidance. I really appreciate your input. I have experience of the B105 SAS mode 20 odd years ago and that would be my frame of reference. The EC135 started out as the BO108 on the drawing board.

So in your experience you think the EC135 SAS is an improvement on the B105 system?

I fully agree that the safest option is with ATT and coupled vertical mode. My problem is I need to justify the extra costs of the ATT.

[skadi]

Because I have no experience with SAS equipped BO 105s, I cant tell you whether its an improvement or not.

skadi

[Sir Niall Dementia]

DB;

The 135 SAS only is way better than the 105. The 135T2 AP is 3 axis only, but in 2 500 hours on them I still reckon one of the best AP's I've ever worked with.

When you get to the T2+ it gets better still as the climb/decsent rate on selecting an altitude is 500' fpm rather than 1000' fpm. A T2 will get mighty close to VNE quite quickly if you don't reign in the descent rate when selecting an altitude to descend to.

I'm not sure how many T2's were built SAS only, but I doubt its' many as the weight penalty of the full system actually isn't that serious, and certainly it makes the ride far more comfortable for the passengers.

If you want more info pm me.

SND

[drakkar]

On the EC135 family, there are several layers of SAS help.
The first is Yaw SAS, it just dampers the yaw
The second is Yaw + pitch and roll, P/R, it's better and you may leave the cyclic some seconds to grab something.
The third is Yaw + P/R + Pitch damper which will authorize you to perform IFR dual pilots.
On top of this the APM 2000 which is a 3 axis auto pilot with upper modes, HDG, IAS, maintaining altitude on the pitch mode but with some safety features if the collective is not high enough.
Now, flying above the sea by CAVOK without SAS is OK, it's like a squirrel, by bad weather conditions, you will find the cost of the APM 2000 secondary compared to the huge safety brought.
The T3H, for Helionix, will be delivered next year and is a 4 axis autopilot.
Drakkar

[skadi]

On the EC135 family, there are several layers of SAS help.
The first is Yaw SAS, it just dampers the yaw
The second is Yaw + pitch and roll, P/R, it's better and you may leave the cyclic some seconds to grab something.
The third is Yaw + P/R + Pitch damper which will authorize you to perform IFR dual pilots.
On top of this the APM 2000 which is a 3 axis auto pilot with upper modes, HDG, IAS, maintaining altitude on the pitch mode but with some safety features if the collective is not high enough.
Now, flying above the sea by CAVOK without SAS is OK, it's like a squirrel, by bad weather conditions, you will find the cost of the APM 2000 secondary compared to the huge safety brought.
The T3H, for Helionix, will be delivered next year and is a 4 axis autopilot.
Drakkar

I have not seen or even flown any 135 with just YAW SAS, i think P/R SAS is just standard equipment.
In my opinion, the difference with or without pitch damper is not remarkable in normal flight operation.

skadi

[thechopper]

If you have to justify the extra cost of reduced workload/increased safety over water, you start lining up the holes in the cheese.
Do you plan with a tailwind both ways as well?

[helisniper]

If this is regarding a serious proposition to operate flights in the scenario you suggest, I suggest you consider which rules the aircraft will be operated under and what the regulatory requirements might be. But for a daylight and VFR only operation you may be okay form the regulatory point of view.

Whether it's sensible is a different thing all together and depends on many things.

[DOUBLE BOGEY]

HELISNIPER - I think I know some of the rules but please elaborate in case I missed something?

Also if you have EC135 SAS mode flight experience I would be grateful if you could share it

[[email protected]]

DB - I wonder if it has to do with SPIFR requirements. Is the proposed operation MP or SP?

[DOUBLE BOGEY]

Hi CRAB,

I was being a little coy. Surely you know enogh about me now to believe I understand the rules well.

Essentially SPIFR requires ATT plus Height and Heading hold.

However SPVFR at night or over the water does not.

There is a strong safety case to say VMC night and overwater flight, both being navigated without reference to visual landmarks, an ATT plus holds is a must. However EU-OPS does not mandate this requirement.

Hence when we consider, in order of importance:

1. SAFETY
2. COMPLIANCE
3. COMMERCIALLY EXPEDIANCE

Flying overwater in a SAS mode machine meets 2 and 3 above. I want to be convinced that it also meets 1 above and with no personal flight experience of the EC135, our ship of choice, hence my rotorheads enquiry on this thread.

Hope this makes more sense now.

[DOUBLE BOGEY]

SND - thanks for your very helpful post.

[DOUBLE BOGEY]

THE CHOPPER - unless you are lucky enough to have un limited budget EVERYTHING has to be justified.

In this case, the rules allow Flight in circumstances I believe most experience pilots would agree, challenges the margins of safety. Sometimes compliance does not always mean SAFE.

I have an open mind but tempered by experience and gut feeling. However, it has to be justified to customers in a marketplace where the guy next door would offer a better, compliant as a maximum, deal.

[[email protected]]

DB - just goes to show that the rules are not infallible - the concept that night overwater is VFR is a nonsense - as anyone who has done it will tell you.

If people argue with your safety concerns regarding the SAS vs ATT question, take them over the water in the dark and ask them what they are looking at to fly the aircraft - it will be the instruments not the external horizon.

I once did a search from Cyprus for several hours in classic Mediterranean goldfish bowl conditions, with a Nav in the LHS talking me onto vessels that we let down to identify to confirm they weren't the one in distress we were looking for. I was working hard (Wessex only had SAS equivalent and a very poor baralt hold) and we decided to head for Paphos for refuel after one more homing. The Nav vectored me onto a light and we started towards it - until he mentioned that it didn't seem to be getting any closer. I looked up and realised we were trying to home to a star and he admitted he had had the leans for the last hour or so. We went home!

We also lost a Wessex overwater at night in the Med after a minor emergency distracted the pilot and he flew into the sea.

Bugger the EASA rules - it is IFR over water at night and the aircraft needs to be properly equipped - Ie SPIFR. Don't wait to lose an aircraft to make your safety case.

[[email protected]]

In fact, I'm sure your FFS must have night capability and possibly overwater as well. Get people to fly a medium workload sortie with the odd minor emergency in SAS mode with no height hold and see what happens.

I took part in a series of simulator test flights many years ago at RAE Bedford to look at handling qualities in DVE (which is what night overwater is) and aircraft stability was the major factor in safety.

[DOUBLE BOGEY]

Hi CRAB for once me and you are in perfect alignment. Quite why the authorities have never fully recognised that there is no such thing as VMC over the water at night, until we see lights AND depth perception, is beyond me. Unfortunately the minimum equipment requirements don't stack up to what you eloquently describe, is the overriding safety case.

UK CAA did make very positives steps to alleviate this after the Mathew Harding accident. They mandated AP for SP Night including over the land. Unfortunately this got overruled when EU-OPS became the law. Maybe Brexit will give them back the teeth they need.

DB