CAT III and turboprops
 

Hi there,

I just surfed the web, but couldn't come up with useful information. Please help me out on this one.

To my knowledge turboprops and most bizjets are not capable of performing cat III approaches. Be it for the lack of autothrottle or autopilot, etc.
I'm thinking of Dash 8, ATR, Citation, Learjets, Kingair, ...

Every now and then one of those shows up for an cat III approach, which makes me wonder. Are there systems or upgrades on the avionics, which can enable aircraft named above of performing cat iii approaches.

If yes, then it would surely be a financial matter. Would it be feasable for airline operators only, or could private an biz a/c operators afford such a step as well.

Thanks for your help,

FR

I could be wrong, but was under the impression that Horizon Air (Alaska Airlines feeder) in the USA does with HUD's low viz approaches lower than Cat II...in the DO-328 and the DHC-8...anybody with facts/details???

The Q400 is certified for CAT III using a headup display system--As previouslsy suggested, Horizon may be using it.

I believe most UK ILS systems are calibrated by a twin turboprop.

There's a slight difference between what a calibration aircraft does and how it's equipped and one that uses an ILS to CAT III minimums in anger.

<<There's a slight difference between what a calibration aircraft does and how it's equipped and one that uses an ILS to CAT III minimums in anger>>

Depends how you view it - OK, the calibrator won't be making an approach "in anger" but it's equipment is, I suspect, far more sophisticated than that on commercial aircraft.

HUD - way to go ! Best thing since wings.
Autothrottle is not required.

Requirements
 

dusk2dawn, you state autothrottle is not required.
Then what is required, resp. what makes it impracticable on turboprop a/c?
Which systems does the HUD substitute?

THX, FR

Saab 2000 Cat III capable too!

:ok:

The requirements for any aircraft to operate in Cat 2/3 conditions are given in the appropriate regulations; JAR-AWO, or AC120-29, etc. These specify the necessary onboard equipment and reliability, the latter may include the aircraft systems – dual electrical systems etc. Thus, any suitably equipped aircraft can fly in low vis conditions, the type and extent of equipment determines the lowest minima that may be used.

In Europe, there were differences between commercial operations and ‘bizjet’ aircraft, although these were generally in operational approval. The operational requirements for Cat 2/3 are now standardised in JAR-OPS1 and the revised AC120-29 series.

In Europe a commercial operator has to gain approval from his authority before commencing operations; I think that this includes a list of airfields/runways to be used for Cat 2/3 operations and an agreement from the airport / country involved; thus ATC should be aware of the operator's capability / approval.

Gen'understood that CAT3 are 'performed'with autopilot and'AUTOLAND'...Alasks and others recieved aproval for lower than CAT2 by having HUD to supplement the anto pilot at 80'TSO for the landing (flare)part of the approach. The B727,and early B737 didn't have Autoland,hence the Hybrid Cat3.......
With the advent of the B767 and later the majority of Transports utilized 'Fail operational'autopilot autoland....
The continued HUD developement today is to cater to none autoland aircraft ,below the 737 ????
The FAA have approved private operations of CAT2 for years,as long as the autopilot was 'cert' to the 80'disconnect-for a manual landing..:ok:

FoxRomeo ,

Well, first of all we did not have autothrottles on the B727 with CAT III HUD, thus I assume it is not required.

Secondly, the impracticality of a CAT II/III system very rapidly turns into a question of money.

Finally, the HUD does not substitute any systems, it is a complex add-on wich may be cheaper than a CAT II/III certified autopilot, but probably only if such an autopilot does not exist for the type in question.

Didn't the French Postal Service routinely drive the F-27 down to the ground years ago? I forget the exact procedure, but they carried a third pilot in the jumpseat who decided whether the landing went ahead or not.

Hmmm, seems to me the 'ole HS121 Trident AND the Lockheed TriStar qualified
 

<With the advent of the B767 and later the majority of Transports utilized 'Fail operational'autopilot autoland....>

Fail operational was certainly available on the L1011, long before the B767.



Anyone who has flown the 'ole Lockheed tri-motor will recognize that it simply sets the standard by which others hope to achieve, with autolands...CATIII or not.

Only the RAF seemed to have a 'slight difficulty' with the L10...and one pilot in particular.:{

And...Pigboat remembers well.
The French postal service did indeed perform CATIII with F.27's...manually flown as I recall.

HD, that was my point really. To compare a calibration aircraft (that I don't think is approved for operational CAT III anyway) with routine turbo-prop CAT III ops is apples and oranges.

411,your absolutely right I'd forgotten that I'd witnessed an 'Autoland'(from the jumpseat)on the L1011(circa1972)..CYVR..
ATC only turned us onto final about 6 out,hooked up the autopilot,and did an excellent capture and landing....
I believe Aeropostal shot very low approaches in the overnight mail DC3's.....
:ok:

No \'authorized\'autoland on the,but it has been pointed out to me that if one waits (hooked up to the ILS)until 50\'and then one selects \'Altitude Hold\'the a/craft does n nice Flare...:D :D

Caravan-that is!!!:confused:

As I've actually helped certify a CAT IIIa system on an RJ (the Flight Dynamics, now Rockwell-Collins, Head Up Guidance System or HGS) maybe I can explain. This the same system as used on the dash8-400 and RJ-700 flown by Horizon.

In the 60s, most CAT III landing systems were of the Autopilot/Autoland type which normally needs a triplicated type of architecture to meet the reliability numbers. In the UK aircraft with this were the H-S Trident & BAC 1-11 using Smiths systems.

In the US, the Tristar, 747 & DC-10 all had Autopilot-based systems but, for the DC-9, Douglas collaborated with Sundstrand to certify a "hybrid" CAT IIIa system. This, in essence took a normal two channel Autopilot and monitored it via a HUD which also allowed the pilot to keep looking outside - making looking for the runway a much easier job.

Flight Dynamics took this idea a stage further and used data from the ILS and IRS to generate guidance that aloows the pilot to continue the approach to a 50 feet Decision Height (CAT IIIa). The pilot's performance - how close he is following guidance - is monitored by both the HGS Computer and the Co-Pilot using his instruments. Autothrottle is not required - or fitted - but speed control to within 5 kt is the hardest part of the task.

The turboprop you see is probably using a similar IRS-based system but for a different purpose. He is calibrating the ILS beam by flying down it to a known point on the runway. The inertial data is integrated to provide a record of the actual aircraft position on the approach which is compared with the beam data to see if it is within ICAO limits or needs to be adjusted.

ICT_SLB covered the essentials.
Thank you all for your help so far.
I got myself the JAR-OPS and the AC120-29 which answered many of the questions.

I found it interesting to read about the "work-arounds" (e.g. the HUD or the third pilot in the cockpit).

Keep them up there,

FR

Fox Romeo,
If you're more interested in the systems side, you need to look at JAR AWO - specifically Sub-Part 4 for Category III.

For a look at the future, go here - ARINC is now coming up with a standard HUD that will be in the majority of new aircraft including the A380.