Displaced ILS question
 

Hope you don't mind me asking this question here but some of you know my "name" as a regular on Capcon.

I was taking a look at the AIP entry for Lydd and noticed that the ILS loc was off to the side of the rwy rather than on the centreline and that it was had a 5 deg offset. I presume it's put to the side so that the offset loc beam is directly over the runway touchdown point?

My question is when you clever lads and lasses fly an ILS like this do you kick off the offset in the same way you would do with the drift from a crosswind approach or is there a different way of touching down off that ILS.

I did also see that the remarks state no auto coupled approaches allowed below 250ft but that makes sense, after all you don't want to end up in a field beside the ILS loc aerial.

Just fly it in the normal way and as soon as you get enough visual reference position the aircraft in the same way as you would on a normal visual approach.

The DA of 430 FT ( 418 DH ) is a long way above the ILS system minima, I am guessing that along with the modest runway approach lighting the FAT ofset is the reason for the DH being 218 ft above the ILS system minima to enable time for the visual maneuver.

Thanks.

Didn't think of checking the minimums etc.

Just as well I failed the eyesight test in the PPL medical then :E

Hey, Clicker

You are keeping us all honest.

Thank you!

:ok:

The worst offset ILS I encountered in my career was the old Hong Kong airport at Kai Tak...... r'way 13
Here is an interesting wikipedia of that approach using offset ILS.

"The landing approach using runway 13 at Kai Tak was spectacular and world-famous. To land on runway 13, an aircraft first took a descent heading northeast. The aircraft would pass over the crowded harbour, and then the very densely populated areas of Western Kowloon. This leg of the approach was guided by an IGS (Instrument Guidance System, a modified ILS) after 1974.
Upon reaching a small hill marked with a huge "aviation orange" and white checkerboard used as a visual reference point on the final approach (in addition to the middle marker on the Instrument Guidance System), the pilot needed to make a 47° visual right turn to line up with the runway and complete the final leg. The aircraft would be just two nautical miles (3.7 km) from touchdown, at a height of less than 1,000 feet (300 m) when the turn was made. Typically the plane would enter the final right turn at a height of about 650 feet (200 m) and exit it at a height of 140 feet (43 m) to line up with the runway. This manoeuver has become widely known in the piloting community as the "Hong Kong Turn" or "Checkerboard Turn". Amongst passengers it became known as the "Kai Tak Heart Attack".[18]
Landing the runway 13 approach was already difficult with normal crosswinds since even if the wind direction was constant, it was changing relative to the aircraft during the 47° visual right turn. The landing would become even more challenging when crosswinds from the northeast were strong and gusty during typhoons. The mountain range northeast of the airport also makes wind vary greatly in both speed and direction. From a spectator's point of view, watching large Boeing 747s banking at low altitudes and taking big crab angles during their final approaches was quite thrilling. Despite the difficulty, the runway 13 approach was nonetheless used most of the time due to the prevailing wind direction in Hong Kong.
Due to the turn in final approach, ILS was not available for runway 13 and landings had to follow a visual approach. This made the runway unusable in low visibility conditions."

We used to do this on B707 in typhoon conditions but stopped when big fanjets were used as the fan could not handle the shifting winds.

I've seen a video of that HKK approach. Scary or what. Left at the flats, right at the boards. That said as I like flying I would loved to have been in a jump seat for that.

While I failed that medical I did work for an airline for 7 years (ops at LGW) so managed a few jump seat trips, always interesting. Gets too boring in the back, I prefer to know where I am.

Wish I had, every time I flew :}

Not trying to be a smartass clicker but Hong Kong designator is HKG...HKK is Hokitika in New Zealand.

I'm saying this because my wife's galpal visited us in Bali recently. Trouble is... she booked her flight to Balikpapan!
There was confusion between my wife and her pal on facetime until I said "just cancel your BPN destination and book to DPS." Which is Denpasar, Bali's airport.
Sometimes airport designators, on the internet, are easier to identify than airport names.

I also recall some honeymoon couple booked what they thought was a flight from UK to Sydney, Australia but wrote Sidney, which is in BC, Canada. They wondered why there was a stopover in Nova Scotia.:confused:
The good news....when everyone in Canada learned of their misfortune, they became celebrities and had the best honeymoon and memory of it.

I suggest you stick to the small aircraft as per your hobby...the big ships in the sky are boring and automated. In a few years I predict they will be flown like drones....they already test driverless cars.
A friend of mine has one that parks itself....we're nearly there!

Don't have a plate in front of me at the the moment, but is the reason for the offset LOC at Lydd not due to the presence of the prohibited area for the Nuclear power station nearby? If it was a direct LOC i think it would take you through the prohibited area.

Standing by to be corrected...

OH

Kai Tak
 

I always thought that we would land with laundry on the starboard wing tip one day off the lights on top of the flats.

It looked worse than it probably was but not in a x-wind when the turn could so easily be overcooked. I lived in the 18 floor of the apartment block with a view of the checker board and have witnessed many who turned too soon and couldn't get back to the 130deg centre line and gone around.
The CX guys, more familiar with the approach than others, let the A/C go closer to the checker board and, given the wind prevailed from N.E., let it help in the turn and cut down the angle to line-up.
The offset IGS was only used to avoid obstructions and get down to minimum...the rest was the old grunt style of flying by the pants.

Clicker ...

IIRC the 5 ̊offset is to keep the RWY 21 ILS approach clear of the D141 (Army Ranges)

See Plate Notes re intercept at 900m before THR

http://i1004.photobucket.com/albums/...psfd924913.jpg

Credit : NATS Doc - Not For Navigation

Missed approach requires a Right Turn to avoid the Power Station and Army Ranges shown.

More here ...

NATS Lydd EGMD

Davita, Reminds me of a new FO in a well known UK airline whose bidline seniority was not conducive to going anywhere desirable. He was, therefore, surprised and delighted when he was awarded the tripline for which he'd bid containing two LOS flights.

Clue: It ain't LA :E

Sumburgh has offset LLZs on both runways; Odiham has one too on runway 27.
They're not uncommon but can never be Cat 1 and the minimum DH is 250ft as opposed to 200ft with an inline Cat 1 LLZ.

Davita

That will teach me to rely on my memory without checking!

Coff,

Thanks I had discounted the power station from the ILS side having visited the area's RSPB reserve there trying to photograph a Bittern there. Heard it booming but never saw it.

Had also forgotten about the Lydd ranges although had used the area to help train some air cadets for a couple of Nijmegen marches back in the 70's.

Gaydon had an in-line and an offset on the same runway. Only had markers on the in-line.

Coff, beg to differ?

Runway QFU is 203 and the FAT of ILS is 208.

So, it is offset towards D141, not away from it.

My suggestion would be that this is due to the higher ground to the west of the FAT. 208 seems to coincide with the lowest of some pretty high ground.

ISTR the RADALT drops quite low when you fly this approach.

Cheers.

Nice Castle,

I thought that was possible but also noticed that the GP is set at 3.5 so assumed that was for the height clearance.

After your suggestion what now puzzles me is the RNAV procedure sets the inbound track nearer to one of the summit of one of the hills you mention than the ILS procedure does.

Hmm. Well, there is probably more to the installation and offset reasoning than meets the eye. Yes, 3.5 deg definitely due to that ridge line. I concede that the inbound arc also tracks you directly over the high ground as well, whichever way you arrive?
But it's not D141 that drives the offset.

Oh, and the RNAV approach has a very steep approach angle, recommended at 478 ft per nm, so what, about 4.5-5 degrees?