[Ricci]

Originally Posted by jinojohnt

Cool hobby. I am also fascinated by planes.
I have a few questions:
1. Why is it that planes have only three sets of wheels (like an autorickshaw) and not four sets of wheels?

Usually there's no place wide enough for the 4th. Some planes like the Antonov giants - An-124 and An-225 have 4-wheels on 2 front struts though, it's rarely useful on anything else than wide, huge cargo planes.

2. Why do planes land on rear wheels first? Is it possible to land 'nose first' if we had 2 sets of strong wheels in the front?

That's because the main gear is stronger and designed to take the impact. The CG is closer to the main gear, which are usually 2-6 sets and spread wide in order to provide stability, too narrow and the aircraft could topple.

The reverse used to the the case in older places, upto the 1950s which had the engines in front, thus most of the weight being in front and necessitating the main undercarriage to be in front.

Modern aircraft are usually jets and have more of their weight (the C of G) in the centre, with engines usually wing mounted , in some cases, rear-mounted hence the tricycle type undercarriage.

There are piston engined aircraft with the modern tricycle type gear - paired main wheels behind and single nose wheel front, but this is rare.


3. Why is it that cars have 3 point seat belts, but planes have only a lap belt?

Cost cutting - no? The main role of seat belts in planes is passenger retention in case of turbulence, not crash protection from the seat in front, as in cars. Three point belts also will slow down passenger evacuation, which by law is supposed to be done in 90 seconds start to end in emergency.

4. Why is it that planes need to be 'taxied' to the runway using pushback tractors? Why can't the plane move on it's own?

Most planes do taxi on own power, they're just reversed out of the apron by tractors. Taxiing is the most inefficient stage, jet engines have rather high fuel consumption at idle to low rpm, so it's preferred to have the tractor pull them to the taxiway at least.

5. While landing, when the wheels touch the ground, there's so much friction and smoke because of the stationary wheels touching the ground at high speed. Won't this problem be solved if the wheels are rotated just before landing (to prevent many tire-burst-accidents)?
6. How is the body of the plane able to balance itself on the wings during a flight, as the tail and the nose of the plane have different weights?

Weight. Motors to rotate the wheels will be used only on landing but need to be carried all the time. Aircraft designs go to extra-ordinary lengths to save weight. The cost saving in tyre life is probably not sufficient over the life-cycle of a plane to justify it.

My answers inline and in bold.

[Jeroen]

A couple of additional comments

Originally Posted by Ricci

2. Why do planes land on rear wheels first? Is it possible to land 'nose first' if we had 2 sets of strong wheels in the front?

That's because the main gear is stronger and designed to take the impact. The CG is closer to the main gear, which are usually 2-6 sets and spread wide in order to provide stability, too narrow and the aircraft could topple.

The reverse used to the the case in older places, upto the 1950s which had the engines in front, thus most of the weight being in front and necessitating the main undercarriage to be in front.

Modern aircraft are usually jets and have more of their weight (the C of G) in the centre, with engines usually wing mounted , in some cases, rear-mounted hence the tricycle type undercarriage.

There are piston engined aircraft with the modern tricycle type gear - paired main wheels behind and single nose wheel front, but this is rare.

You are showing pictures of planes desigend before the second world war (Spitfire) and during the second world war (Bell Cobra) things have moved on since, landing gear wise.

Most single pistion engine aircraft since the mid 60's have tricycle type gear. I.e. Cessna, Cirrus, Mooney, Diamonds etc. etc. For the last three decades I would say properly 98% of pilots learned to fly, obtained their PPL, on a tricycle type gear of plane. Handling a tail wheel mounted plane, or a tail dragger as they are commonly refered to, requires more skill and practice. In general you will find lots of people in the aviation community who will still promote getting a tail dragger endorsement on your pilot's license as it is known. All about rudder and stick techniques. I've flown a few hours in these (Boeing Stearman), great fun but very different if you are used to regular tricycle gear. Here's a nice article: http://airfactsjournal.com/2013/08/n...wheel-that-is/
and here's a little more a tail dragger technique http://airfactsjournal.com/2013/08/w...a-taildragger/

The reason planes land on their main gear under the wing is twofold, as pointed out that is where more or less the centre gravity is, but also aerodynamic design of the plane requires it to be in a nose up attitude to be able to generate sufficient lift

Originally Posted by Ricci

3. Why is it that cars have 3 point seat belts, but planes have only a lap belt?

Cost cutting - no? The main role of seat belts in planes is passenger retention in case of turbulence, not crash protection from the seat in front, as in cars. Three point belts also will slow down passenger evacuation, which by law is supposed to be done in 90 seconds start to end in emergency.

Pilots on all commercial planes wear full body harness, lap and shoulder straps. I have piloted planes were the pilot only wears a lap strap (Cessna C150, a three point belt (e.g. Cessna 172, Cardinal,) and full body harnass (e.g. Cirrus SR20/22)

There is sufficient evidence that having passenger belt up properly would reduce fatalities/injuries greatly in plane crashes. But it would require a complete redesign of the seats. it would also come at a considerable weight penalty.

Originally Posted by Ricci

4. Why is it that planes need to be 'taxied' to the runway using pushback tractors? Why can't the plane move on it's own?

Most planes do taxi on own power, they're just reversed out of the apron by tractors. Taxiing is the most inefficient stage, jet engines have rather high fuel consumption at idle to low rpm, so it's preferred to have the tractor pull them to the taxiway at least.

Actually, quite a few jet and propellor planes are capable of reversing out of a gate under their own power by using reverse thrust. It is very rarely used. Very few airlines and or airport authorities allow it. Mainly because of safety reasons. You blow a lot of dust and sand towards the terminal building. and on the engines for that matter which can lead to substantial damage. When reverse thrusters are used during landing to assist braking, they typically get stowed as soon as the speed drops below approx 80 knots.

On some planes that do have reverse thrust capability it is explicitly forbidden under any and all circumstances as deploying reverse thrust whilst at stand still might cause the plane to lift it's nose and slam its tail into the ground.

You can find several youtube video, but again in practice very rate to see planes reversing out of their stand.

Jeroen

[Ricci]

Originally Posted by Jeroen

A couple of additional comments
You are showing pictures of planes desigend before the second world war (Spitfire) and during the second world war (Bell Cobra) things have moved on since, landing gear wise.

Most single pistion engine aircraft since the mid 60's have tricycle type gear. I.e. Cessna, Cirrus, Mooney, Diamonds etc. etc.

The pictures are for illustration purposes only, whatever I could find quickly, was not deliberately looking for WW2 era only.

Originally Posted by Jeroen

The reason planes land on their main gear under the wing is twofold, as pointed out that is where more or less the centre gravity is, but also aerodynamic design of the plane requires it to be in a nose up attitude to be able to generate sufficient lift

Yes, but then tail-draggers already have the angle-of-attack above zero while tricycle types need to pull up (some do have a slight nose up attitude on the ground designed in, though , several fighters prominently so). Having a tricycle helps handling at those speeds, being more stable nose up. The CG hasn't really shifted much with the engine still up front, so the centre of lift too cannot move too far back. So , these aircraft need to keep a short wheelbase , but I think the main reason is handling - it's easier for pilots to learn and does not affect visibility as with tail-draggers. Plus, the wheelbase is shorter, so they are more nimble in the taxiway.

Originally Posted by Jeroen

Pilots on all commercial planes wear full body harness, lap and shoulder straps. I have piloted planes were the pilot only wears a lap strap (Cessna C150, a three point belt (e.g. Cessna 172, Cardinal,) and full body harnass (e.g. Cirrus SR20/22)

Pilots of course, I believe the OP asked about passenger planes, so I surmise the focus is on passenger seatbelts rather than pilots.

Originally Posted by Jeroen

There is sufficient evidence that having passenger belt up properly would reduce fatalities/injuries greatly in plane crashes. But it would require a complete redesign of the seats. it would also come at a considerable weight penalty.

Yes, needless to say. As long as the anchor is built into the seat, there shouldn't be any redesign required for the plane itself, only the seats and that extra nylon belt and mechanism will add maybe a couple of hundred kg, not unmanageable given the variation in passenger+luggage weight. I think it's entirely for ease of use esp during evacuation that they don't employ more restrictive but safer harness.

Originally Posted by Jeroen

Actually, quite a few jet and propellor planes are capable of reversing out of a gate under their own power by using reverse thrust. It is very rarely used. Very few airlines and or airport authorities allow it.

You can find several Youtube video, but again in practice very rate to see planes reversing out of their stand.

Jeroen

I do know most plane engines have reverse thrust ability, I didn't know it was prohibited by airports (using reverse thrust), I thought it was merely a practice to both save fuel and reduce noise level close to the terminal. Yes, there is some safety risk given there will be ground crew in the vicinity and assorted ground vehicles, like the stair gantry or fuel trucks.

There's lot of raised eyebrows over the Saab AJ37 Viggen and its antics with the reverse thruster

[Jeroen]

Originally Posted by Ricci

Pilots of course, I believe the OP asked about passenger planes, so I surmise the focus is on passenger seatbelts rather than pilots.

That's why I started my reply with

A couple of additional comments

To add even further, in some of those planes I quoted the passengers also have three point belts / full harness.

Here some more developments: Cirrus will fit as standard on their new jet, AOS seat belts (http://generalaviationnews.com/2014/...os-seat-belts/) Essentially seat belts with built in air bags, for pilots and passengers

Similar belts are already fitted to earlier Cirrus models.

Have a look at the AOS websit and you will see how the rich of this world get belted up and how us, the plebs, on regular commercial planes get belted up:

http://www.aviationoccupantsafety.co...ntegrated.html

Originally Posted by Ricci

As long as the anchor is built into the seat, there shouldn't be any redesign required for the plane itself, only the seats and that extra nylon belt and mechanism will add maybe a couple of hundred kg, not unmanageable given the variation in passenger+luggage weight. I think it's entirely for ease of use esp during evacuation that they don't employ more restrictive but safer harness.

I very much doubt that. It most likely will require a complete redesign of the chair and the anchor points on the cabin floor, including maybe redesign of the structural parts of the floor. All or parts of the structure of the plane need relooking due to different stresses that will occur due to different seat belt design.

With a three point belt, the anchor point for the shoulder point will be much higher, so the back of the seat needs to be redesigned and this higher anchor point will also give a higher moment on the anchor points during a crash.

Also, whether it's a little or a lot of redesign, the seat, it construction, including the anchoring to the cabin floor and the cabin floor itself would have to be completely re-certified. A very tedious, lengthy and thus expensive process.

Originally Posted by Ricci

I do know most plane engines have reverse thrust ability, I didn't know it was prohibited by airports (using reverse thrust), I thought it was merely a practice to both save fuel and reduce noise level close to the terminal. Yes, there is some safety risk given there will be ground crew in the vicinity and assorted ground vehicles, like the stair gantry or fuel trucks.

Here is an interesting video of a (turbine) prop plane reversing under own power:

https://www.youtube.com/watch?v=macvyCmdA3I

And here is a DC9 reversing away from the gate under its own power. Keep you eye on the left engine, at 0.11 you can clearly see the reverser bucket popping up at the back end of the engine

https://www.youtube.com/watch?v=mO-FdDKxuNU

Jeroen

[mmxylorider]

For those of you in the Los Angeles area, Santa Monica airport has a pretty neat observation area for people to watch planes in motion. This airport does not cater to the big jets, but recreational single/double piston engine 4-8 seater and small jets like bombardier/gulfstream usage can be seen. There are some private charter running scheduled services and one can watch significant activity during morning hours on Saturday.

[Jeroen]

Originally Posted by mmxylorider

For those of you in the Los Angeles area, Santa Monica airport has a pretty neat observation area for people to watch planes in motion. This airport does not cater to the big jets, but recreational single/double piston engine 4-8 seater and small jets like bombardier/gulfstream usage can be seen. There are some private charter running scheduled services and one can watch significant activity during morning hours on Saturday.

Thanks for sharing. Just to add for the plane spotter enthusiast:

Not wanting to sound to nationalistic, but Amsterdam airport is probably one of the best, if not the best place to watch a hugely busy international commercial airport.

Here a google map showing most of the spotter places:

https://www.google.com/maps/d/u/0/vi...c.kiu0HqS5EhtI

All are well accessible and on some of the larger ones, you might even find little mobile cafeteria where you can get a snack and a drink.

The largest one has an actual McDonalds:

http://www.mcdonaldsrestaurant.nl/sc...schiphol-noord and also here on the official Amsterdam website: http://www.schiphol.nl/Travellers/Sh...ipholWhere.htm

So you can take the whole family; kids eating their happy-meals, while you sip a cup of undefined muck that McDonalds universally flogs as coffee. But you will have planes taking off / landing every three minutes only a few hundred meters from where you are sitting. And just about any commercial plane comes to Amsterdam airport. So you will see anything from a Fokker 50 to an Airbus 380 or Boeing 747-400 and anything and everything in between.

And it gets even better at the terminal. Here in India only passengers are allowed inside the terminal building. On most western type of airports, everybody is allowed in the terminal to drop off or pick up passengers.

Amsterdam airport has a huge general area, called the Plaza. http://www.schiphol.nl/Travellers/Sh...ipholPlaza.htm

More shops then I've seen in any Indian mall. Also there are several restaurants and bars, open to the public where you can overlook the terminal area.

There is also a huge panorama terrace, open to the general public, on top of the terminal building where you can go outside and watch the planes taxing to and from the gates, getting fuelled, loaded up with luggage etc.

http://www.schiphol.nl/Travellers/Sh...amaTerrace.htm

http://www.virtualtourist.com/travel...race-BR-1.html

Apparently, the have also put a real Fokker 50 on the terrace recently, which again is open all free of charge to the public. I haven't seen this yet, as I've been outside the Netherlands for more then 6 years now. So these days I only do Amsterdam Airport as a passenger.

So, apart from a very busy international hub airport, Amsterdam-Schiphol airport is a huge tourist attraction. Every weekend it attracts thousands of people, whole families, who come and enjoy walking around the airport, do a bit of shopping, eat and drink, whilst getting very close up to the planes.

And for the real aviation enthusiast, only a 10 minutes drive away from Amsterdam Airport, the best aviation store in the world as well:

http://www.aviationmegastore.com/inf...e64744a7cb7e0f

What these guys don't stock or have on display is simply not worth having. Everything on aviation, ready made models, model kits, books, magazine, flight simulation, charts, navigation equipment etc. etc

I never spend less then two hours in this shop when I visit and it's only a thirty minutes drive from where we lived (near the Hague), so I go there often!

Enjoy!!

Jeroen

[TKMCE]

For those people residing in India, Kochi Airport has a very good viewing area. It is the top level of the terminal above the international wing (Kochi is a single building - domestic and international terminals are actually two wings of the same building). Entrance ticket is Rs 50 and you may have to show some ID proof as well. Both the ticket counter and the entrance to the viewing gallery are well marked.

This facility is well maintained. There are clean washrooms, a more than adequate snack bar and the area is spacious and regularly cleaned. I have taken my child there three or four times already.

Be aware that since the area is above the international wing, you will have to chose your time carefully. Most international departures at Kochi are from midnight to 6 AM which is not practical for spotting. Howver beween 08 AM and 12 Noon you can see quite a few international departures of Air India and Air India Express including that rare aircraft (nowadays) an Air India Boeing 747 landing by 10 AM on Thursdays and Sundays. If you can go on a Thursday at these times, you will also see a Saudia Airbus A 330 and an Emirates Boeing 777 along with some colourful Boeing 737s of Air India Express. The whole gamut of domestic flights can also been seen taxing although they park at the domestic terminal at the other end.

[Ricci]

Originally Posted by Jeroen

Cirrus will fit as standard on their new jet, AOS seat belts (http://generalaviationnews.com/2014/...os-seat-belts/) Essentially seat belts with built in air bags, for pilots and passengers

Similar belts are already fitted to earlier Cirrus models.
--SNIP--
how the rich of this world get belted up and how us, the plebs, on regular commercial planes get belted up

Thanks, that was interesting, airbags in passenger jets. It will be effective for crash landings (up to a point of course). I wonder if the rich will eventually get altogether different aircraft, for those who don't have their own private jets.

Originally Posted by Jeroen

I very much doubt that. It most likely will require a complete redesign of the chair and the anchor points on the cabin floor, including maybe redesign of the structural parts of the floor.
Also, whether it's a little or a lot of redesign, the seat, it construction, including the anchoring to the cabin floor and the cabin floor itself would have to be completely re-certified. A very tedious, lengthy and thus expensive process.

I'm not sure how they'll implement it since the cabins have no pillars and luggage rack extends only a limited amount. The seat height will need to be increased to accommodate taller occupants ; maybe a mechanism to adjust the height can be added with a weight penalty.

Re-certification is always going to be long and costly process, no doubt.

Originally Posted by Jeroen

Not wanting to sound to nationalistic, but Amsterdam airport is probably one of the best, if not the best place to watch a hugely busy international commercial airport.

Never been there sadly, it is rated one of the top 5 often. Maybe I should find work with a Dutch org.

Originally Posted by Jeroen

And it gets even better at the terminal. Here in India only passengers are allowed inside the terminal building. On most western type of airports, everybody is allowed in the terminal to drop off or pick up passengers.
There is also a huge panorama terrace, open to the general public, on top of the terminal building where you can go outside and watch the planes taxing to and from the gates, getting fuelled, loaded up with luggage etc.

Overly-security conscious, and if you are spotted taking photographs, you'll be given dirty looks too, and likely have cops question you like a terror suspect.

Originally Posted by Jeroen

Apparently, the have also put a real Fokker 50 on the terrace recently, which again is open all free of charge to the public.

There is a 747 near Stockholm Arlanda airport, I believe it's been converted to a hotel/dorm unless I'm confusing it for another plane-to-hotel conversion.

Originally Posted by Jeroen

And for the real aviation enthusiast, only a 10 minutes drive away from Amsterdam Airport, the best aviation store in the world as well:
http://www.aviationmegastore.com/inf...e64744a7cb7e0f

What these guys don't stock or have on display is simply not worth having. Everything on aviation, ready made models, model kits, books, magazine, flight simulation, charts, navigation equipment etc. etc

Thanks, will take a look !

[Jeroen]

Originally Posted by Ricci

T
There is a 747 near Stockholm Arlanda airport, I believe it's been converted to a hotel/dorm unless I'm confusing it for another plane-to-hotel conversion.

Yes, that's right. I work for a Swedish firm, so I get to go to Stockholm a lot. I've seen this 747 hotel, its just outside the airport. Never been in it though.

The Fokker at Amsterdam airport is still in original condition, so you get a good impression of what these planes looked like inside and outside. Fokker was a bit of one of the Dutch national prides. But of course, it went belly up quite some time ago. KLM used various Fokker models extensively over the years. So its a bit of a national treasure at our national airport.

Jeroen

[mikon]

AA @ CDG Airport

[swiftdiesel]

Just spotted an Antonov 124 take off from Chennai. Is this airport cleared for super jumbo jets? Unfortunately, couldn't click a pic but I have a screenshot from Flightradar24. Honestly, never expected to catch an Antonov 124 on a casual evening in Chennai. Hope to catch it another time with a camera!

[slicvic]

Originally Posted by swiftdiesel

Just spotted an Antonov 124 take off from Chennai. Is this airport cleared for super jumbo jets? Unfortunately, couldn't click a pic but I have a screenshot from Flightradar24. Honestly, never expected to catch an Antonov 124 on a casual evening in Chennai. Hope to catch it another time with a camera!

Looks like its a regular visitor

http://www.youtube.com/watch?v=ezXE2CQuKpE

This is from Jan 2017

[swiftdiesel]

Originally Posted by slicvic

Looks like its a regular visitor

This is from Jan 2017

Wow didn't know that, thanks! Any means to find its next scheduled stop in Chennai? TIA!

[slicvic]

Originally Posted by swiftdiesel

Wow didn't know that, thanks! Any means to find its next scheduled stop in Chennai? TIA!

I found that video with a google search of "AN 124 MAA"

AN 124 means large large cargo right, maybe zauba or similar sites will help identifying such shipments

[swiftdiesel]

Originally Posted by slicvic

I found that video with a google search of "AN 124 MAA"

AN 124 means large large cargo right, maybe zauba or similar sites will help identifying such shipments

Yeah I can do that. Thanks very much!