[audioholic]

The reversal of the signal is a very simple thing from a technical point of view. But what still surprises me is, why they chose an antenna or a transmission source that generates significant sidelobes. They should be suppressed such that its intensity is a fraction of that of the main lobe.

For those who are wanting to know why this can happen, the GS signal consists of a 150Hz and a 90Hz signal which is beamed along the Glideslope. The intensity of the signal is compared to maintain it through the GS. When the intensity of both signals are equal, that means the aircraft is in line with the GS. So if the intensity 150hz signal is higher, the aircraft should go up, ie below the GS and vice versa.

The transmitting antenna has a main lobe of the combination of the two signals. Due to its design it also radiates side lobes of the same 150-90hz signal. When the aircraft flies above the actual GS, it tends to capture 150Hz of the upper side lobe and 90hz of the main lobe. Thos causes the whole logic to be inverted. As the 150hz signal gets more and more intense, the aircraft will point higher thinking it is below the GS whereas it will be the opposite actually.
Attaching an image for understanding:

Source: http://i.stack.imgur.com/v5ap5.gif

[Jeroen]

Here's a bit of amazing footage! I've seen videos before of very large commercial planes that started pitching up due to severe winds, but this is truly something else!

https://www.youtube.com/watch?v=b_WmjWAGkLI#t=95

[Jeroen]

Just to add to the ILS discussion earlier in this thread: In the USA there are more then twice as many WAAS approaches as ILS approaches. So flying a GPS approach is the name of the game, rather then ILS these days.

Below a little video of a GPS approach. I'll leave it for everybody to comment on how well this crew does. In essence everything that I pointed out you need to do to ensure you are on a ILS approach is still valid for GPS approaches as well. However, there is no danger of false lobes. But you still need to verify with all means available that you are flying a correct altitudes, speed, descent rates etc.

Before I left the USA I was flying this type of plane, although this is a slightly more recent version. It gives a good impression on what a modern Glass Cockpit looks like and what goes on during the approach. Believe it or not, but this so called Garmin Perspective Glass Cockpit provides a much more intuitive and comprehensive presentation of data and options than the FMS of say a 747-400.
enjoy:

https://www.youtube.com/watch?v=hbogZJVfuF8

Jeroen

[Jeroen]

Here's a very cool video of the Boeing Dreamliner 787-9 being put through it's paces. Some very impressive flying and equally impressive video footage!

http://dcnewsroom.blogspot.in/2014/0...earsal_13.html

Wish I could be at the Farnborough show this year.

Jeroen

[audioholic]

Originally Posted by Jeroen

Here's a very cool video of the Boeing Dreamliner 787-9 being put through it's paces. Some very impressive flying and equally impressive video footage!

http://dcnewsroom.blogspot.in/2014/0...earsal_13.html

Wish I could be at the Farnborough show this year.

Jeroen

Impressive. The aircraft looks very agile(or not sure if the camera is ). I was awestruck by the A380 doing a similar show. In this video the best part I liked was the near vertical takeoff. That happened in the initial days of flight simulator for me. Lift nose up and leave the elevator controls as it is

[Jeroen]

Originally Posted by audioholic

Impressive. The aircraft looks very agile(or not sure if the camera is ). I was awestruck by the A380 doing a similar show. In this video the best part I liked was the near vertical takeoff. That happened in the initial days of flight simulator for me. Lift nose up and leave the elevator controls as it is

Apparently, this was a practice run for their display at the Farnborough air show.

Here is the same routine at the actual air show yesterday:

https://m.youtube.com/watch?v=vzr313wSY_Y

Twin engine commercial planes are capable of very impressive climbs as demonstrated. For these routines they will ensure the plane is as light as they can make it with very little fuel on board. Instant near vertical climb!

[desertfox]

In India you still have to land on so many airports on VOR or at best CAT I the upgradation process is so slow.

In Patna 12 airbus A 320 ( 2 out of them A 319 ) flights land and take off daily on 5400 ft of runway.

[Jeroen]

Originally Posted by desertfox

In India you still have to land on so many airports on VOR or at best CAT I the upgradation process is so slow.

In Patna 12 airbus A 320 ( 2 out of them A 319 ) flights land and take off daily on 5400 ft of runway.

Thanks. Having only a VOR or a CAT 1 is quite a difference. CAT 1 is actually the most basic of ILS landings. Higher CAT means lower of no Decision Height and less runway visual range or even none.

It's not just the airport that needs to be upgraded. Higher CAT landings also put additional requirements on the instruments on the plane as well on the pilot training and formal training. On the ground it also requires various upgrades, notably the runway lighting system becomes more and more elaborate and powerful. Just a little anorak fact, on so called non-towered airports the pilots can light the runway lighting remotely by clicking their mike several times. number of clicks determines the intensity.

You would be surprised how little runway an airbus or even a Boeing 747 need at low weights. Check this https://theflyingengineer.files.word...ment_744er.jpg A 747 can take of from this runway too.

Other factors are obviously altitude, air pressure, air temperature and wind speed and direction.

Jeroen

[desertfox]

I know it can but if a take off fails in a Delhi bound A320 in Patna with 180 passengers, 7 crew 12 MT of Luggage and 8 MT of Fuel then there is little hope with 5400 ft of runway.

[Jeroen]

Originally Posted by desertfox

I know it can but if a take off fails in a Delhi bound A320 in Patna with 180 passengers, 7 crew 12 MT of Luggage and 8 MT of Fuel then there is little hope with 5400 ft of runway.

take off performance calculations take all of that into account. So for a given situation, (weight, wind, runway contamination etc) the runway length is calculated to include sufficient length to abort the take off up to the decision speed v1. So when a plane takes off at a short or a long runway that doesn't make a difference on the safety of being able to stop in case of an emergency prior to reaching V1. Pilot or dispatch will do these calculation prior take off together with some other calculations such as weight and balance, fuel (reserve fuel) etc.

Jeroen

[BoneCollector]

Originally Posted by desertfox

I know it can but if a take off fails in a Delhi bound A320 in Patna with 180 passengers, 7 crew 12 MT of Luggage and 8 MT of Fuel then there is little hope with 5400 ft of runway.

As of today, all flights in and out of Patna are flying with a load penalty of 20%. So at max they are taking is 154-156 passengers. Yes, indeed the runway is quite short but the planes land with higher engine speed as made out by the sound than what you'll find in Delhi. The take off starts with full on brakes and throttle and the plane doesn't roll but starts with a jerk. I do have a video of a take off of an airbus 320 from tarmac while disembarking from another flight but couldn't find it to upload. JetAirways flys its B-737-700 at the most. I'm yet to see a B-737-800 or 900 in Patna. Airbus A-319 & 320 are frequent here with Indigo, GoAir and Air India using them.

And pray to God that another Alliance Air type mishap doesn't happen here.

Alliance Air Flight 7412
https://en.wikipedia.org/wiki/Alliance_Air_Flight_7412

[Jeroen]

Originally Posted by BoneCollector

As of today, all flights in and out of Patna are flying with a load penalty of 20%. So at max they are taking is 154-156 passengers. Yes, indeed the runway is quite short but the planes land with higher engine speed as made out by the sound than what you'll find in Delhi. The take off starts with full on brakes and throttle and the plane doesn't roll but starts with a jerk. I do have a video of a take off of an airbus 320 from tarmac while disembarking from another flight but couldn't find it to upload. JetAirways flys its B-737-700 at the most. I'm yet to see a B-737-800 or 900 in Patna. Airbus A-319 & 320 are frequent here with Indigo, GoAir and Air India using them.

And pray to God that another Alliance Air type mishap doesn't happen here.

Alliance Air Flight 7412
https://en.wikipedia.org/wiki/Alliance_Air_Flight_7412

Not sure what you mean by landing with higher engines speed? The take off as you describe is a standard short runway technique that all planes/ pilots will follow. (Commercial as well as GA, e.g. I would follow the same procedure in.my one engined plane if I had to take off on a short runway). Short runway being a relative term here, relating to a particular plane and its take off capabilitites.

For commercial planes, as I said earlier, whatever runway length, must comply with requirements to make a safe and full stop, before reaching V1 in case of an abort.

Jeroen

[BoneCollector]

Originally Posted by Jeroen

Not sure what you mean by landing with higher engines speed?

Jeroen

With that what I meant was, when a plane comes to land in at Patna airport, the engine sound is harsh compared to when the same plane lands at Delhi. My guess is entirely on engine sound, just a speculation as am not an airline pilot! ☺

[Jeroen]

Originally Posted by BoneCollector

With that what I meant was, when a plane comes to land in at Patna airport, the engine sound is harsh compared to when the same plane lands at Delhi. My guess is entirely on engine sound, just a speculation as am not an airline pilot! ☺

Well, sounds can be misleading I guess.
Landing speeds of planes are dictated by a few relevant things such altitude (barometric pressure), weight and flap settings. For a short runway you will be using the highest flap setting and for a given landing weight that will give you a certain landing speed. Note that landing speed is an "air speed" so the speed of the plane through the air, not ground speed.

So if you have a lot of nose wind the ground speed in the final approach is less, as it is airspeed that keeps you from stalling.

Jeroen

[Jaguar]

Of late, I have seen the Indigo A320s make an annoying humming noise during take off. The noise gradually reduces once the aircraft reaches cruising altitude. I heard this noise on 4 different occasions on 2 different sectors. So the chances of me flying the same plane was quite slim. Any idea what this noise could be?