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Engineer defends concept circular runway idea

bbc.co.uk

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Re: Engineer defends concept circular runway idea

#31

Post by exabrial »

astrodust wrote: post #24
exabrial wrote: post #18

Earlier quoted context omitted.

Correct me if I'm wrong, but I thought the whole idea behind the circular part was so that doing a crosswind landing would be "easier", because you could setup the landing so the crosswind pushes your towards the center...

If the wind cooperates and goes in a single direction during landing, sure, but why does nature have to be so kind? There can be pretty severe shear at different altitudes on the way down, and the wind can flip direction any time it wants.

thanks, good explanation

Re: Engineer defends concept circular runway idea

#32

Post by Scarblac »

mrfusion wrote: post #17

I'm thinking if we ever figure out a way to reduce airport foot prints it could drastically drop housing costs. There are hundreds? Of acres of prime urbanish land. Look at Boston for example. I wonder if they take the opportunity cost of having an airport there into the cost of flying? That land could be worth 100 billion??

I think this will happen naturally, as we will have to limit the number of flights due to CO2 constraints.

Re: Engineer defends concept circular runway idea

#33

Post by tropo »

rpmcmurphy wrote: post #15
esemor wrote: post #4

As an airline pilot flying Boeing 757 and 767 I think this concept is really cool but it does overlook some fundamental principles of the unreliability of weather in order to be practical. This week I have landed in variable winds gusting up to 45 knots and then every inch of wingtip clerance counts, a drawback of this design. What if the aircraft makes a long landing (floats) and suddely faces a different wind compo…

I am also a pilot. I'll add to this by explaining a couple of basic principles in flying aircraft. The #1 reason this is a very bad idea is it is not compatible with flying what's called a stabilized approach, which is fundamental to safe landings. What this means simply is you fly your last (final) leg of approach on a straight line aligned with the centerline at a shallow glide angle. The moment before touch down y…

I don't think you need to "go from wings level to a banked turn at exactly the right moment" for this. There are two ways to make it work.

As proposed, the runway is banked. You bank your aircraft well above the runway surface. You fly above the runway, possibly following it as your holding pattern prior to landing. You can keep going around, banked already. When it is your time to land, you continue around in that bank and descend to the runway.

Alternately, it could be unbanked with straight landings. This makes the circle considerably thicker. Landing is quite normal, aside from the runway markings.

BTW, your "kick out of the crab angle just prior to touchdown" method may be standard, but it is pretty bad. The B-52 gets this right, with 4 pairs of wheels that touch the ground at the same time and are all capable of being rotated.

Re: Engineer defends concept circular runway idea

#34

Post by rpmcmurphy »

tropo wrote: post #33
rpmcmurphy wrote: post #15

Earlier quoted context omitted.

I am also a pilot. I'll add to this by explaining a couple of basic principles in flying aircraft. The #1 reason this is a very bad idea is it is not compatible with flying what's called a stabilized approach, which is fundamental to safe landings. What this means simply is you fly your last (final) leg of approach on a straight line aligned with the centerline at a shallow glide angle. The moment before touch down y…

I don't think you need to "go from wings level to a banked turn at exactly the right moment" for this. There are two ways to make it work. As proposed, the runway is banked. You bank your aircraft well above the runway surface. You fly above the runway, possibly following it as your holding pattern prior to landing. You can keep going around, banked already. When it is your time to land, you continue around in that b…

The whole point of a stabilized approach is to avoid unnecessary maneuvers in the final moments of flight, and to simplify decision making. Your approach is a straight in powered glide. If you like where you end up, you cut power, flare and land. If you don't like the situation, you apply full power and climb straight ahead, then turn according to the rejected landing procedure for the runway or ATC instructions.

What you describe needlessly adds complication to the approach, which adds risk, which will certainly result in accidents and fatalities. It's just a bad idea, and there is a reason airport designers never considered this (it is not as if the idea of banked curved roadways is new).

Sorry as a pilot, I can say this is not just a bad idea, it is a lethally bad idea. A fun simulator challenge, but not something that will work in the real world. If you are doubtful, I would suggest you try circling around a point in IFR conditions within 50' lateral tolerance above a circular runway. Be sure to add zero visibility and a 10-20 knot cross wind to simulate doing so in the clouds above the runway as you descend.

Re: Engineer defends concept circular runway idea

#35

Post by dragonwriter »

rpmcmurphy wrote: post #34
tropo wrote: post #33

Earlier quoted context omitted.

I don't think you need to "go from wings level to a banked turn at exactly the right moment" for this. There are two ways to make it work. As proposed, the runway is banked. You bank your aircraft well above the runway surface. You fly above the runway, possibly following it as your holding pattern prior to landing. You can keep going around, banked already. When it is your time to land, you continue around in that b…

The whole point of a stabilized approach is to avoid unnecessary maneuvers in the final moments of flight, and to simplify decision making. Your approach is a straight in powered glide. If you like where you end up, you cut power, flare and land. If you don't like the situation, you apply full power and climb straight ahead, then turn according to the rejected landing procedure for the runway or ATC instructions. Wha…

> Be sure to add zero visibility and a 10-20 knot cross wind to simulate doing so in the clouds above the runway as you descend.

With a circular approach to a circular runway, aren't all winds cross winds (and, also, headwinds and tailwinds)?

Re: Engineer defends concept circular runway idea

#36

Post by rpmcmurphy »

dragonwriter wrote: post #35
rpmcmurphy wrote: post #34

Earlier quoted context omitted.

The whole point of a stabilized approach is to avoid unnecessary maneuvers in the final moments of flight, and to simplify decision making. Your approach is a straight in powered glide. If you like where you end up, you cut power, flare and land. If you don't like the situation, you apply full power and climb straight ahead, then turn according to the rejected landing procedure for the runway or ATC instructions. Wha…

> Be sure to add zero visibility and a 10-20 knot cross wind to simulate doing so in the clouds above the runway as you descend. With a circular approach to a circular runway, aren't all winds cross winds (and, also, headwinds and tailwinds)?

That was a trick suggestion. Also while dealing with flying the airplane, also be sure to keep track of whether the landing pattern is clockwise, or counter-clockwise, or was it clockwise, and which heading you are currently on and how that relates to your rejected landing turn in case you need it, which you probably will. I don't see what could possibly go wrong.

All I'll say is if I was the head of the programming committee for the air transport association conference, I would invite the designer to keynote, as comic relief.

Re: Engineer defends concept circular runway idea

#37

Post by tropo »

rpmcmurphy wrote: post #36
dragonwriter wrote: post #35

Earlier quoted context omitted.

> Be sure to add zero visibility and a 10-20 knot cross wind to simulate doing so in the clouds above the runway as you descend. With a circular approach to a circular runway, aren't all winds cross winds (and, also, headwinds and tailwinds)?

That was a trick suggestion. Also while dealing with flying the airplane, also be sure to keep track of whether the landing pattern is clockwise, or counter-clockwise, or was it clockwise, and which heading you are currently on and how that relates to your rejected landing turn in case you need it, which you probably will. I don't see what could possibly go wrong. All I'll say is if I was the head of the programming…

I don't see why a human has to do this.

Even if they do, I don't see why it can't be done with an awareness system like the F-35 helmet. That would let you see the outline of the runway through arbitrary fog.

There is no special "rejected landing turn". You rise up just a bit, keep following the runway, and retry when you wish.

Re: Engineer defends concept circular runway idea

#38

Post by tropo »

dragonwriter wrote: post #35
rpmcmurphy wrote: post #34

Earlier quoted context omitted.

The whole point of a stabilized approach is to avoid unnecessary maneuvers in the final moments of flight, and to simplify decision making. Your approach is a straight in powered glide. If you like where you end up, you cut power, flare and land. If you don't like the situation, you apply full power and climb straight ahead, then turn according to the rejected landing procedure for the runway or ATC instructions. Wha…

> Be sure to add zero visibility and a 10-20 knot cross wind to simulate doing so in the clouds above the runway as you descend. With a circular approach to a circular runway, aren't all winds cross winds (and, also, headwinds and tailwinds)?

No. Wind can be circular. For example, right above the runway could be the eyewall of a hurricane.

Re: Engineer defends concept circular runway idea

#39

Post by dragonwriter »

tropo wrote: post #37
rpmcmurphy wrote: post #36

Earlier quoted context omitted.

That was a trick suggestion. Also while dealing with flying the airplane, also be sure to keep track of whether the landing pattern is clockwise, or counter-clockwise, or was it clockwise, and which heading you are currently on and how that relates to your rejected landing turn in case you need it, which you probably will. I don't see what could possibly go wrong. All I'll say is if I was the head of the programming…

I don't see why a human has to do this. Even if they do, I don't see why it can't be done with an awareness system like the F-35 helmet. That would let you see the outline of the runway through arbitrary fog. There is no special "rejected landing turn". You rise up just a bit, keep following the runway, and retry when you wish.

> I don't see why a human has to do this.

Because automated systems fail.

> Even if they do, I don't see why it can't be done with an awareness system like the F-35 helmet.

Because most aircraft aren't F-35s and expenses and fallible systems that are appropriate and sensible for combat aircraft that may have to operate in conditions in which civilian aviation would not aren't necessarily something you want to make civilian aviation dependent on in conditions in which, with sensible things like straight runways, it would not be.

Re: Engineer defends concept circular runway idea

#40

Post by dragonwriter »

tropo wrote: post #38
dragonwriter wrote: post #35

Earlier quoted context omitted.

> Be sure to add zero visibility and a 10-20 knot cross wind to simulate doing so in the clouds above the runway as you descend. With a circular approach to a circular runway, aren't all winds cross winds (and, also, headwinds and tailwinds)?

No. Wind can be circular. For example, right above the runway could be the eyewall of a hurricane.

Good point.

That might produce other problems for landing, though.

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