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Category A Takeoff: Background
Is anyone aware of the history behind the development of the Category A Takeoff. Where it was first developed, who were the development pilots or any information about its origins?
https://lh5.googleusercontent.com/-H...eoff+fig+1.png From an operational point-of-view, has anyone encountered any 'challenges' while performing this manoeuvre? Is there, for example, any collision risk while conducting CAT A departures (especially off-airport) as a result of the restricted rearward field of view? |
Is that a comedy profile? Spot the deliberate mistake..............
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Not intentionally, no. T'was the only illustration I could put my finger on.
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TDP = Takeoff decision point.
LDP = Landing decision point. Is there, for example, any collision risk while conducting CAT A departures (especially off-airport) as a result of the restricted rearward field of view? |
I know that the screen height of 35 feet was based on a double decker bus (at Croydon)
Phil |
Sav,
One would assume that you would have taken a look at the departure/takeoff path beforehand? FM Supplement - NOTE The helipad maneuvering area and takeoff flight path shall be clear of obstacles. |
Was there Life before Cat A?
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SASless, Yes, it was called taking off and going flying. Many moons ago (30years) during my initial S-76A training, Cat A was explained as a selling point since the S-76A was certified for Cat A operations. The RFM included all of the appropriate charts. A close look at the charts revealed that, to meet Cat A requirements at gross weight, one would need an unobstructed helipad about 1500 ft in diameter. That is just what we had at Stratford.
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RV: Agreed.
However, in addition to fixed obstacles I was wondering too about the hypothetical risk in making a rearward vertical takeoff and the potential for climbing into overflying traffic; for example in a rural location on the periphery of a control zone etc. My main interest however is in learning (if possible) 'when and who' were involved in developing this procedure. |
I'd be interested to see some stats showing how many lives have been saved by Cat A in helicopters. I know of only one actual engine failure during a takeoff and that wasn't being flown under Cat A because the S76 was not capable in the conditions required by the operation. The aircraft was safely landed.
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one would need an unobstructed helipad about 1500 ft in diameter |
Then you would have used a DHC6 Twin Otter because it could lift more out of the same space! When Shell Oil (Nigeria) went from Bell 212's to the EC-155....the Heliports became runways....that should tell you something about the effects of using Cat A profiles and performance. I have practiced the "Reverse" Takeoff Profile....never ever did one for real in daily operations. Also did some very convoluted gyrations in other aircraft that were supposed to provide for Cat A performance (with a very limited weight allowed) as well....but in the end would have been far happier just flying the machine like a helicopter it was. I was never on a Civliian operation where an engine failure on Takeoff ever occurred....not that they do not.....just they never did anywhere I was based. |
The helipad Cat A was around in the mid/late 70s and became part of British Airways procedures offshore on the Brent platforms with their large unobstructed decks (Brent B in particular). The diagram in the OP is not very representative as most profiles are far more vertical than is shown: the criteria is to keep the helipad visual through the chin window, not out of the front screen! We dabbled with the idea in BEAS 212s, but with rig shuttles and 5 minute turnarounds it wasn't deemed practical plus many of our into wind profiles didn't allow a back up.
The BA S61 drivers (when introduced to the procedure about 1977 or 78) actually started using it off the runway at Sumburgh, which seemed a strange thing to do with thousands of feet of reject area ahead on departure. I've found the biggest challenge to be getting pilots to understand the overall concept along with judging the TDP properly. Once that hurdle is overcome then there is no real issue in carrying out the procedure. |
Hi Savoia
I believe that the rearward take off profile was produced to allow the mirror newspaper group to fly the printing plates from the rooftop helipad at their London office to the printing presses in Manchester. It's quite possible that I am talking bolloxs though! Cheers TeeS |
Originally Posted by TeeS
(Post 8179760)
It's quite possible that I am talking bolloxs though
The FAA produced a paper in 1991, Helicopter Rejected Airspace Takeoff Airspace Requirements which seems to be addressing the problems of too-steep departure paths and a more flexible airspace system to allow for this. Prior to this report, the helicopter manufacturers were following the fixed wing criteria laid down by the FAA (IIRC). |
Originally Posted by TeeS
(Post 8179760)
Hi Savoia I believe that the rearward take off profile was produced to allow the mirror newspaper group to fly the printing plates from the rooftop helipad at their London office to the printing presses in Manchester. It's quite possible that I am talking bolloxs though! Does anyone recall who Maxwell's driver was at the time, we are talking mid-to-late 80's?
Originally Posted by Savoia
(Post 7669376)
https://lh5.googleusercontent.com/-m...y+Lakin%29.jpg
AS355F1 G-RMGN atop 'Maxwell House' in 1987 (Photo: Gary Lakin) Here G-RMGN seen atop the former 'Mirror Group Newpapers' office aka 'Maxwell House' at no. 8 New Fetter Lane. |
Thanks Savoia
Hopefully I'm not entirely senile yet then. It may have been Flight International that had an article about the development of the profile and I would guess that was, as you say, around the mid-late 80's TeeS |
We pre-dated the London rooftop departures by 10 years or so with Cat A in the NS.
My copy of the 212 manual with Cat A profiles (including Vertical Takeoff Profile) has the revision dated in September 1976, with the original having been published in August 1972. Forget the idea of the Mirror being at the forefront of this := |
Originally Posted by John Eacott
(Post 8179832)
Forget the idea of the Mirror being at the forefront of this := Do you suppose it began with one of the manufacturers? |
Hi John
Thanks to the wonders of the digital World, I have found the article that led me to believe the procedure was developed for the Mirror Group operation. It makes quite interesting reading, if only for the dream of masses of rooftop helipads in central London. I now realise that the article doesn't claim this was the first use of helipad profiles (Worldwide) but you might see where my confusion started. Hopefully this link will work: 1985 | 2964 | Flight Archive Cheers TeeS |
I first landed on the IPC roof in London in January 1975 in a Bo105D - can't remember any formal Cat A being in force for that type at that time. In fact in wasn't until four years later in June 1979 that I flew some rooftop take off single engine failure assessment flights on a 105DB with George Locke (ex-CO D Squadron at Boscombe Down) who was MD of Helicopter Marketing, the MBB sales agents in the UK at that time.
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Well done Tees! :ok:
Mike Barrett, McAlpine Helicopter's chief pilot, sees the UK Civil Aviation Authority attitude to helicopter operations as enlightened, compared with the restrictive regulations in other European countries. After an initial period of reservation, the CAA has been practical and co-operative in establishing criteria for the newspaper operation. McAlpine is confident that city rooftop pads have significant advantages over ground-level pads for safety, environmental, and utility reasons. The elevated platform allows improved clearance of surrounding obstructions, particularly in the event of engine failure during approach or departure. It ensures low noise disturbance (amazingly, this operation has received almost no noise complaints from local residents in more than three years). Rooftop platforms may come in handy for rapid fire and medical evacuation. Few buildings in London's crowded skyline are stressed to take the weight of helicopter. Many roofs are cluttered with air-conditioning vents, railings, and other impedimenta which would make even an emergency landing a hazardous undertaking. Perhaps designers of city tower blocks should give thought to the beneficial role that the helicopter can play as a public service vehicle. This is one of the fastest growing areas of helicopter usage in the USA today. CAA regulations stipulate that the diameter of an elevated pad should be at least 2 times that of the helicopter's rotor—some 88ft in the case of the Twin Squirrel. In addition, the pilot must be able to lift-off from the pad to a Critical Decision Point (CDP) 90ft above the pad elevation, lose one engine, and either land safely clear of the building or continue with a single-engined departure without sinking to less than 35ft above pad elevation. The square International Press Centre roof measures 46ft x 46ft, and the Twin Squirrel, with its 35ft rotor diameter, can meet neither requirement with a normal lift-off technique. McAlpine Helicopters has developed special procedures to meet the CAA criteria. These have been demonstrated to, and approved by, the CAA, and involve a lift-off to 15ft above the pad, followed by a climb in backward flight, keeping the pad in sight through the pilot's lower right-hand windshield. This reverse climb is continued to the 90ft CDP. Single-engine safety is vital In the event of an engine failure below this point, the pilot uses the departure pad as his emergency landing area. Should failure occur after CDP, a transition into descending forward flight is made, maintaining the minimum 35ft margin above roof elevation while accelerating to the take-off safety speed (Vtoss) of 40kt. Under IFR conditions the pilot must fly level, accelerating further to his best singleengined climb speed of 55kt (Vy), before starting his en-route climb. Under VFR, 40kt will be maintained in the climb until 550ft above departure elevation, before acceleration to 55kt. Similar criteria apply for approach and landing, with a Landing Decision Point (LDP) 90ft above pad elevation. Engine failure above LDP entails a missed approach procedure, similar to the departure profile. Below LDP power loss entails landing on to the roof. https://lh6.googleusercontent.com/-D...re+profile.png Before landing on the IPC, pilots take an engine condition reading to ensure full engine performance before starting an approach, wind 8mb off the London QNH (equal to the 240ft height of the helipad building), and then make an approach into wind (using local chimney smoke, or the flags on the Houses of Parliament two miles away) to land on the nearest into wind diagonal line across the roof. This ensures the maximum landing dispersion distance, which allows leeway for the pilot's fore/aft touchdown error. To the passenger the landing appears dramatic and, indeed, there is little room for error. Despite this, McAlpine research and development pilot Geoffrey Holder makes the technique look easy. He has played a major part in developing the rooftop techniques to the standards required by the CAA. Up to three passengers can be carried from the roof, together with the plates. In fact, there needs to be at least one passenger, in the copilot's seat, to prevent an aft e.g. position allowing the tail boom to strike the edge of the building. |
The rearwards departure from a helipad is normal for a number of other helicopters (I do at least one almost every working day).
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Originally Posted by Savoia
(Post 8179032)
Is anyone aware of the history behind the development of the Category A Takeoff. Where it was first developed, who were the development pilots or any information about its origins?
The FAA had approved Cat A for the Bell 212 in 1972, so any development would have been well in place before that. The attached scans indicate both the approval date of the Cat A Supplement (18th August 1972) and the profile: http://www.eacott.com.au/gallery/d/5...t+A+title.jpeg http://www.eacott.com.au/gallery/d/5...A+profile.jpeg I think it somewhat cheeky for the Flight article to infer that McAlpine had developed this technique some 13 years after this Bell 212 example, even allowing for journalistic license. I'm sure that there would be other examples prior to the 212, certainly the S61. |
John Boy.....the FAA lead the CAA in something as sophisticated as this.....really?:E
We all know that the Yanks could not possibly understand the finer points of helicopter flying!:ugh: |
Originally Posted by SASless
(Post 8180107)
We all know that the Yanks could not possibly understand the finer points of helicopter flying!:ugh:
Originally Posted by paco
(Post 8179109)
I know that the screen height of 35 feet was based on a double decker bus (at Croydon)
Phil |
Belgrano House....sounds like a deep water Reef!
Sadly....the Brits were quite late to the party....and have had great success imitating more progressive nations re rotary wing flight. Seems the Russians and Germans led the way. A History of Helicopter Flight |
John - the bus was used for fixed wing, and we know the helicopter stuff was pinched from there :)
Phil |
They might have led the way in writing about it Sasless but actually applying it is another matter.
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A fairly simple question but ... as so often happens here, it quickly becomes another tree against which the old dogs rush to cock their legs. :rolleyes:
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dubious maths
seems like dubious maths to expose the aircaft (and it's other sytems) to such a prolonged vunerable state for the theoretical upside of being able to crash gently back on the pad if it's the engine that fails in this time frame.
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John: Thanks for the info on the 212. Would be interesting to read a more detailed instruction of the recommended procedure.
Perhaps then it was one of the Bell test pilots who developed the original CAT A takeoff?
Originally Posted by AnFI
(Post 8181242)
seems like dubious maths to expose the aircaft (and it's other sytems) to such a prolonged vunerable state for the theoretical upside of being able to crash gently back on the pad if it's the engine that fails in this time frame.
I believe 'low level, gain speed, then climb' departures are still used from airports (see below): But CAT A (reversing style) are carried-out from helipads (from 02:05): |
Just browsed by this thread and wanted to pass on my thoughts:
The first category a helicopter was the S61, which was certified in the early 1960s. It was a CAM 7 certified helicopter, the predecessor to FAR Part 29, and so it was certified to airline transport requirements. This meant that the FAA had to synthesize requirements that were similar to the Part 25 airplane airline transport requirements. Part 25 requirements had engine failure on takeoff, rotation speeds, accelerate stop distances, and takeoff distances. All were specified using careful flight test procedures. The Category A procedures used for the S61 family included a runway procedure and elevated heliport procedures. The elevated heliport procedures were used for the very first transport operations between the Pan Am building in downtown New York and the New York world's fair Pavilion in Flushing Meadows, New York. The test pilots who performed these procedures told tales of flying over 1000 takeoffs and landings as part of the certification effort. I met Jim Plackis the other day, he was the FAA test pilot on these operations. The S61 was the precursor to all these Category A operations that are now standard for part 29 helicopters. http://blog.modernmechanix.com/mags/...4/heliport.jpg |
Nick thank you.
Just to confirm then, for the record as it were, that what is now the Helicopter Category A departure (rooftop/helipad style) finds its origins in the work of Sikorsky's test pilots (including Jim Plackis) in the 1960's flying the S61? |
Savoia, To my knowledge, the S61 was the first Airline Transport helo, and had the first Cat A procedural approval, in either 1961 or 62. It was quickly (within a few months!) followed by a vertol machine, I believe the civil Vertol 107.
Here is a link to the historic archived TCDS, dated 11/1/1961, and including Cat A procedures: Type Certificate Data Sheet 1H15 The Bell 212 Cat A was dated 6/30/1971: Type Certificate Data Sheet H4SW The V-107 1/26/1962:Type Certificate Data Sheet 1H16 |
Any successful cases?
Savoia - yes you are right that is the 'rationale'
There must have been some successful outcomes of an engine failing at the higher end of the back-up phase, say 50ft of say 90ft. Are there any examples known here by ppruners? How did they fare? I heard of an engine failure on climb out in a single in 1974, the outcome was successful. I love the history - you can feel the optimism! Roof top restaurant heliport - marvelous! Of course back then engines weren't so reliable and they were running singles almost flatout to takeoff, making it even more attractive to have 2 engines. |
CAT A
Nick, you are amazing.
Since I went to high school in Brooklyn, I can legally say, " You da man "! |
John,
Nick did not win the Barnes Wallis Award because of his mere good looks and charm...(sounds of coughing heard)!:ok: |
Nick,
Nice to see you posting again: but the photo of the NY World Fair reminded me that I visited it (the World Fair) in 1965, and I wasn't aware of the helipad until your post :cool: How time flies when you're having fun ;) |
Any known cases?
there must be some known cases of this proceedure working? Shirley?
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