Airplane Landing Questions -- How can the pilot see the ground?

In summary, the process of landing an airplane involves slowing down, lowering the landing gear and flaps, and lining up with the runway. In good weather, pilots use visual indicators while in bad weather they rely on electronic glide slopes. All airplanes, regardless of size, follow the same slope during landing. In modern airplanes, pilots can see the runway ahead, but this was not always the case in older airplanes. Commercial airliners have an altitude call out system for the final approach, using a radar altimeter to measure the height above the runway. In some situations, such as at certain airports, smaller aircraft may use a steeper slope to avoid wake turbulence from larger aircraft. Emergency takeoffs during landings are known as go-arounds,
  • #1
seazal
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The most nervous moments for me is during airplane landing when I'm concerned if the plane would just stall or hit the concrete so hard. So let me take this opportunity to understand it.

How many commercial airliners use manual and automatic landing technology (in terms of percentage)?

For manual. During landing the nose is pointed up, so how can the pilot sees the ground ahead? Do they just guess how many distances to the ground?

Or do they depend on altimeter? Are these so sensitive it can differentiate between 2 meters or 3 meters? Does it work by measuring the force of gravity or air pressure?

For automatic landing, the angle and descent speed is decided by computers? I remember in Die Hard 3, the height was modified by computer and it crash landed. I can remember the part during every landing giving me some kind of landing phobia.
 
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  • #2
The process of landing starts several miles before the runway. The pilot slows the airplane to the proper speed, puts the landing gear down, puts the flaps down, and lines up with the runway. A typical speed when getting close to the runway is 30% faster than stall speed, or a little faster in rough conditions. They fly a prescribed slope. In good weather, there are visual indicators in addition to knowing the proper sight picture. In bad weather, they have an electronic glide slope.

All airplanes, from a two seat Cessna to a huge Airbus A380, fly the same slope, although at different speeds.

upload_2018-12-27_18-9-34.png


In modern airplanes, the pilot can see the runway ahead when flaring for a landing. That was not the case for many pre World War II small airplanes, where the pilot needed to have good peripheral vision and situational awareness.
 

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  • #3
seazal said:
During landing the nose is pointed up, so how can the pilot sees the ground ahead? Do they just guess how many distances to the ground?
Here is the hit list when I googled Pilot's View When Landing an Airplane:

https://www.google.com/search?q=pil...airplane&ie=utf-8&oe=utf-8&client=firefox-b-1

That should help to put your mind at ease a bit, I hope. :smile:
 
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  • #4
Large commercial aircraft have an altitude call out system that uses a radar altimeter to call out the height above the runway during the final phase of landing approach.

jrmichler said:
All airplanes, from a two seat Cessna to a huge Airbus A380, fly the same slope, although at different speeds.
Not always, at some airports, such as John Wayne in Orange County California, the smaller aircraft use a steeper slope on approach to avoid any wake turbulence left behind by a large aircraft landing on the adjacent runway.
 
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  • #5
About a decade ago. I rode an airplane where inches away from touchdown, it took off again with full afterburners (?) on, what situation calls for such emergency take off during landing?

I remembered a china airliner where the same thing happened but it didn't have enough power to take off again after near landing, it just dropped and exploded killing all on broad.

What phase of airplane riding are you concerned the most? Or do you just avoid riding airliner?
 
  • #6
seazal said:
About a decade ago. I rode an airplane where inches away from touchdown, it took off again with full afterburners (?) on, what situation calls for such emergency take off during landing?

Missed approaches that can possibly lead to a go-around... .

Here's some good examples... . :wink:

.
 
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  • #7
seazal said:
what situation calls for such emergency take off during landing?
It's not an emergency, it's a "go-around". I had to go around once when another airplane pulled onto the runway when I was on short final. It was not dangerous, I was at flying speed in a faster airplane and the other plane was just starting from a dead stop. Fortunately, one of us was looking out the windshield.

Airline pilots are taught to go around if the approach is not fully stabilized. If they are a little fast or slow, a little high or low, a little off to one side, they are supposed to go around and get the airplane lined up better the next time.
 
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  • #8
seazal said:
About a decade ago. I rode an airplane where inches away from touchdown, it took off again with full afterburners (?) on...
No, commercial airliners don't have afterburners. That was just full power.
What phase of airplane riding are you concerned the most? Or do you just avoid riding airliner?
I love flying and fly as much as I can (I'm currently taking lessons), so I don't get "concerned" in normal situations. But statistically the landing is the most dangerous:

phase_en.gif
 

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  • #9
seazal said:
The most nervous moments for me is during airplane landing when I'm concerned if the plane would just stall or hit the concrete so hard. So let me take this opportunity to understand it.

seazal said:
[snip]
What phase of airplane riding are you concerned the most? Or do you just avoid riding airliner?

Along with the excellent posts above consider the physics as an aircraft transitions from flight to a surface https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics)

Ground effects tend to cushion and support large aircraft so-to-speak, so relax and enjoy your flights. As the wiki article describes, entering ground effect gives pilots more effective lift and thrust control.
 
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  • #10
russ_watters said:
No, commercial airliners don't have afterburners. That was just full power.

Yep, although full TO/GA power in a modern twin engine airliner certainly feels impressive, especially with the aircraft at a fairly light gross weight (as it usually is when landing)
 
  • #11
cjl said:
Yep, although full TO/GA power in a modern twin engine airliner certainly feels impressive, especially with the aircraft at a fairly light gross weight (as it usually is when landing)
Question: for a go-around, is that "full" as in full? I have trouble wrapping my head around the idea that (as I understand it), they do not apply full power at takeoff, but only as much power as is required for the conditions.
 
  • #12
Just wanted to add..

Contrary to popular opinion landings in an airliner aren't meant to be some sort of soft floaty experience. Its meant to be reasonably "positive" or even "firm". Remember you can't use the wheel brakes while floating along with no weight on the wheels.

Aborted landings are nothing to fear. Whatever the reason I'm quite happy for a pilot to make a positive decision to go around and come back in 15mins. See it as a good thing. Last one that happened to me was due to a small thunder cloud lingering a bit too close to the airfield.

Decades ago planes flew a lot lower and you experience a lot more turbulence at low altitude. Almost every flight had some bumps, but you got used to it and didn't worry. These days planes fly much higher and turbulence is less frequent up there so people tend not to have experienced it much. They sometimes over react when it does occur. Old hands just pull their belt a bit tighter and order another Martini.

I flew gliders for several years and have had many flights in light aircraft, seaplanes, airliners and even one in an airship. I feel far safer in any of these than I do 6ft up a ladder.
 
  • #13
For a go-around, it would usually be full power, yes (with a couple minor caveats that "full power" is actually a software setting in the engine, and the exact same engine may have different "full power" settings depending on what airframe it's hung on and what use case the operator has). You'll see either a switch or a position on the throttles marked as TOGA or TO/GA (for Take Off/Go Around) on modern airliners, and if you're near the ground and have a reason to go around, you'll usually want as much extra energy as possible.

You're right about the takeoff too - derated takeoffs are very common because they save a lot of wear and tear on the engines. A slightly lower turbine inlet temperature really can extend the life of the hot section of the engine, and they still plan it to have plenty of margin for aborts if necessary.

Oh, and Cwatters, unless you're really rather ancient, chances are airline cruising altitudes are about the same as they've been for your whole life. Cruising altitudes have been in the ~28-40k ft range since about the DC-8/707/Convair 880, all of which entered service in the late 1950s. Weather forecasting and radar have gotten much better though, allowing airliners to more successfully navigate around turbulence, and airliner control systems have gotten a lot better at damping it out.
 
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  • #14
I read this: https://en.wikipedia.org/wiki/China_Northern_Airlines_Flight_6901

"While on final approach, the autopilot automatically disconnected. The Captain proceeded to reengage it, believing that it would still be in APP mode. When activated however, the autopilot went into VERT SPD mode with a setting of -800 feet per minute. The crew's failure to disconnect the autopilot and manually land the airplane contributed to the accident. Another factor was the crew's lack of proficiency in English. When the GPWS issued an aural alarm, the captain asked his first officer what the words "Pull up" meant. The first officer replied that he did not know. Consequently, the pilots ignored the warnings and failed to correct their excessive rate of descent, causing the plane to strike power lines and a wall before coming down in a field".

Are there landings that uses autopilot?
What does APP mode and VERT SPD mode mean above?

Also doesn't airliner manufacturer change the language to the native's so the user can understand it?
 
  • #15
Yes, autolands are frequently done (and are very safe). APP mode is approach mode, used when the plane is approaching the runway. VERT SPD mode is vertical speed mode, which is designed to simply hold a given vertical speed (in this case, 800 feet per minute down). All air traffic control and airliner controls are done in english, even in non-English speaking countries by convention. This is done so international traffic can understand each other.
 
  • #16
seazal said:
The most nervous moments for me is during airplane landing when I'm concerned if the plane would just stall or hit the concrete so hard.

You've probably felt but were unaware of something called "Ground Effect"
when the plane gets about one wingspan above the ground, the air underneath it has to get squished out from under the wings
raising pressure on bottom side of the wings causing more lift.
Pilot will reduce power and raise the nose to increase drag and dump speed, encouraging the plane to continue on down to the ground..
https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics)

Next time you fly
pick a window seat a row or two behind back edge of the wing.
Pay attention to what goes on as you get over the end of the runway-
As the plane descends toward the runway you'll see those big flaps move back and down changing the wing shape from flat to curved
trapping air underneath the wing as it gets ever closer to the runway.
On a warm humid summer day you'll see vapor trails curl around the flap edges as the air moves from high pressure region ahead of the flap to low pressure behind it, cooling as it goes...
Just watch and ask yourself "why" about everything you notice.

seazal said:
For manual. During landing the nose is pointed up, so how can the pilot sees the ground ahead?
He looks out the side window.

If you like aviation
i recommend reading Charles Lindbergh's "Spirit of St Louis"
he didn't have a forward view at all , only side windows...
the 1956 movie staring James Stewart is also very good, and is on Netflix
 
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  • #17
The term autopilot seems slightly naive on an I-level thread. The old stick and rudder flight controls nearly all channel through sophisticated avionics; so-called fly by wire. Most landing checklists I've seen describe gradual steps and procedures with some inputs into and action taken by autopilot.

JFTR my experience includes 11 years of aerodynamic experiments at NASA wind tunnels then human factor studies using actual flight crews in full-motion flight simulators. The 12' wind tunnel for instance conducts scads of ground effect studies on any external mods to passenger planes. They test everything including runway surfaces, tire materials. The flight sims include actual ATC (air traffic control) operators using stored traffic but real voice commands to the flight crews.

Before that I was a radar jock at an international TRACON and other places. English is the official language of the skies but communication can be difficult particularly considering radio, weather, and background sounds. Saying the Captain 'spoke Chinese' says little about their mother tongue or ability to understand and speak English under stress. I tried to help this kind of problem on my next assignment designing speech networks.
 
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  • #18
jim hardy said:
You've probably felt but were unaware of something called "Ground Effect"
when the plane gets about one wingspan above the ground, the air underneath it has to get squished out from under the wings
raising pressure on bottom side of the wings causing more lift.
Pilot will reduce power and raise the nose to increase drag and dump speed, encouraging the plane to continue on down to the ground..
https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics)

Next time you fly
pick a window seat a row or two behind back edge of the wing.
Pay attention to what goes on as you get over the end of the runway-
As the plane descends toward the runway you'll see those big flaps move back and down changing the wing shape from flat to curved
trapping air underneath the wing as it gets ever closer to the runway.
On a warm humid summer day you'll see vapor trails curl around the flap edges as the air moves from high pressure region ahead of the flap to low pressure behind it, cooling as it goes...
Just watch and ask yourself "why" about everything you notice. He looks out the side window.

If you like aviation
i recommend reading Charles Lindbergh's "Spirit of St Louis"
he didn't have a forward view at all , only side windows...
the 1956 movie staring James Stewart is also very good, and is on Netflix

I never thought Airline pilot cabin has side windows too. Let's go to this Die Hard 2 scene which gives me phobia.



The conversations is "Activate the " " system, re calibrate sea level to minus -200 feet"

What is the " "? All airliners have it too? or just fiction?
 
  • #19
seazal said:
What is the " "?
ILS ? "Instrument Landing System"

a narrow, directional radio beam broadcast from the airport.
If the plane flies right along the beam it'll wind up at the end of the runway at correct altitude.

upload_2018-12-28_19-57-29.png
there's an indicator on the panel something akin to this
upload_2018-12-28_20-2-48.png


pilot flies the plane to keep the two needles in the circle
i tried it a time or two and decided it's a job for the autopilot...
 

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  • #20
seazal said:
The conversations is "Activate the " " system, re calibrate sea level to minus -200 feet"

What is the " "? All airliners have it too? or just fiction?
ILS: Instrument Landing System. There is a screen in front of the pilot with a set of crosshairs that when centered keep the plane on the glideslope. Yes, they all have it.
https://www.skybrary.aero/index.php/Instrument_Landing_System_(ILS)
 
  • #21
ps i hope that wasn't an in-fight movie...
 
  • #22
jim hardy said:
ILS ? "Instrument Landing System"

a narrow, directional radio beam broadcast from the airport.
If the plane flies right along the beam it'll wind up at the end of the runway at correct altitude.

View attachment 236505there's an indicator on the panel something akin to this
View attachment 236506

pilot flies the plane to keep the two needles in the circle
i tried it a time or two and decided it's a job for the autopilot...

I'm reviewing all airliner crashes incidents at https://en.wikipedia.org/wiki/List_of_accidents_and_incidents_involving_airliners_by_location

I don't come across airplane that stalls and falls down during landing. The 30% above stall speed saves the day? But can't a suicidal pilot just adjusts the lever suddenly to below the stall speed during landing?
 
  • #23
seazal said:
I don't come across airplane that stalls and falls down during landing.

Airline disasters are always like dominoes - several little things align and something sets them in motion.

this has caused more than one stall
(annotations mine)

upload_2018-12-28_20-42-49.png


google "windshear"
Let's just say this guy's stall speed is 70
if pilot enters the storm with airspeed of 100
and headwind is 25
his ground speed is 75,
5 above stall. which sounds ok
but it's airspeed that makes lift not groundspeed...
When he transitions from 25 headwind to 25 tailwind with ground speed still at 75
his airspeed falls to 50
so he's at 20 less than stall speed and is in trouble

http://www.aviation-accidents.net/tag/windshear/

If you're interested in aviation you might enjoy Ernest Gann's book "Fate is the Hunter"
a retired airline captain, he wrote his memoirs and discusses such things..
 

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  • #24
jim hardy said:
Airline disasters are always like dominoes - several little things align and something sets them in motion.

this has caused more than one stall
(annotations mine)

View attachment 236508

google "windshear"

If you're interested in aviation you might enjoy Ernest Gann's book "Fate is the Hunter"
a retired airline captain, he wrote his memoirs and discusses such things..

Please suggest books that answer these questions directly:

Before the Wright Brothers, what were the theories why birds fly? When was the airfoil technology or principles first discovered? And why were the Wright Brothers the first one to successfully apply it?

I'm interesting in flight because I am wondering if something similar could occur in the future, where something akin to airfoil principles (analogy wise) can be used in the vacuum (biased by bohmian mechanics) so vacuaplane (instead of airplane) can use it to navigate the stars. References about such from NASA also welcomed.
 
  • #25
  • #26
seazal said:
Please suggest books that answer these questions directly:

Before the Wright Brothers, what were the theories why birds fly? When was the airfoil technology or principles first discovered? And why were the Wright Brothers the first one to successfully apply it?
The Wright Brothers were the first to do scientific (wind tunnel) testing. I'm not sure they discovered the principles of flight, but they did discover what worked and what didn't, from a practical point of view. That's why they succeeded. A good book describing the history, including the failures of their contemporaries is this:
https://www.amazon.com/dp/1476728747/?tag=pfamazon01-20
I'm interesting in flight because I am wondering if something similar could occur in the future, where something akin to airfoil principles (analogy wise) can be used in the vacuum (biased by bohmian mechanics) so vacuaplane (instead of airplane) can use it to navigate the stars. References about such from NASA also welcomed.
No, this has nothing to do with flight and doesn't suggest anything about spaceflight. There's no connection I can see to this topic.
 
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  • #27
seazal said:
Before the Wright Brothers, what were the theories why birds fly? When was the airfoil technology or principles first discovered? And why were the Wright Brothers the first one to successfully apply it?

i'd start here

https://www.pbs.org/wgbh/nova/wright/resources.html
 
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  • #28
russ_watters said:
The Wright Brothers were the first to do scientific (wind tunnel) testing. I'm not sure they discovered the principles of flight, but they did discover what worked and what didn't, from a practical point of view. That's why they succeeded. A good book describing the history, including the failures of their contemporaries is this:
https://www.amazon.com/dp/1476728747/?tag=pfamazon01-20

No, this has nothing to do with flight and doesn't suggest anything about spaceflight. There's no connection I can see to this topic.

Air is so light. It is still amazing to think it can lift thousands of tons of metal (like the Space Shuttle) via airfoil principles. Vacuum is so light (but don't forget the incredible density of the vacuum for example the alleged 120 magnitude difference to measured value), so it is unthinkable it's not possible to make use of it. If Bohmian Mechanics were true. Won't it change the principles of the vacuum? I know this is a QM question, but just noting both air and vacuum are both light.

Anyway. What is the minimum density of air before airplane is even possible. Can't airplane work in Mars or venus?
 
  • #29
seazal said:
Air is so light. It is still amazing to think it can lift thousands of tons of metal (like the Space Shuttle) via airfoil principles. Vacuum is so light (but don't forget the incredible density of the vacuum for example the alleged 120 magnitude difference to measured value), so it is unthinkable it's not possible to make use of it.
No, the vacuum isn't dense, regardless of what this 120 magnitude difference you speak of is. By definition, there is nothing there to make use of.
If Bohmian Mechanics were true. Won't it change the principles of the vacuum?
No.
Anyway. What is the minimum density of air before airplane is even possible. Can't airplane work in Mars or venus?
Venus, no problem (for a few seconds before it melts), Mars, it would take a very large an light airplane.
 
  • #30
russ_watters said:
No, the vacuum isn't dense, regardless of what this 120 magnitude difference you speak of is. By definition, there is nothing there to make use of.

No.

Venus, no problem (for a few seconds before it melts), Mars, it would take a very large an light airplane.

Is there any relationship between our breathing and airplane? I mean. For air dense enough to fill our lungs, the same air can lift wings. Is it possible for biology to evolve such that we don't need such dense air to breath, and so can live without possibilities of any airplanes?

In a planet where airplanes can't exist. Then I guess most have to travel by boat only. Is it not. Or can rocket engines as transportation work without airfoil technology too?
 
  • #31
seazal said:
Is there any relationship between our breathing and airplane? I mean. For air dense enough to fill our lungs, the same air can lift wings.
Yes, that's more or less true.
Is it possible for biology to evolve such that we don't need such dense air to breath...
Yes, evidently the Nepalese have evolved to be better able to deal with lower air density than most people.
...and so can live without possibilities of any airplanes?
I can't parse that.
In a planet where airplanes can't exist. Then I guess most have to travel by boat only. Is it not. Or can rocket engines as transportation work without airfoil technology too?
Rocket engines work best where there is no air at all.
 
  • #32
Just wondering about this. Is it allowable in airport to bring parachute in bag pack? (for those who have phobia about airplane crashes who would like to bring parachute just in case)?

And for those learning to fly small airplane (with or without propellers). Can't you use or deploy parachute during emergency? This is a reasonable safety device and question.
 
  • #33
If you cannot trust the aircraft and the crew you should not be aboard.
Carrying a parachute onto a commercial flight is an indication of irrational behaviour.
 
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  • #34
Baluncore said:
If you cannot trust the aircraft and the crew you should not be aboard.
Carrying a parachute onto a commercial flight is an indication of irrational behaviour.

But is it illegal? What is the smallest parachute backpack one can bring onboard a commercial aircraft. What does aviation regulation actually says about this? Just asking.
 
  • #35
seazal said:
Just wondering about this. Is it allowable in airport to bring parachute in bag pack? (for those who have phobia about airplane crashes who would like to bring parachute just in case)?

Sure you can take one. However:

1) Airliners aren't designed for people to jump out of. The cabin is pressurised and the doors typically open inwards - so you can't easily open the doors to jump out.

2) Airliners can cruise at 35,000ft. If you jumped out at that height you would probably die unless you also had an oxygen system. Even if you free fall I don't think you can't get down fast enough to avoid suffocation.

3) If the aircraft is out of control you won't be able to get your chute out of the overhead, strap it on and casually walk to the door. You will most likely be experiencing very high g forces as the aircraft tumbles. If the aircraft is under control, why jump out of it? Far safer to stay in the aircraft.

4) Most accidents occur during take off or landing. You would have to be wearing your chute and stood by the open door waiting to jump just in case. And what if you can't jump because you are too low before realising there is a problem? You would be safer strapped into your seat.

5) Most of the planet is covered by ocean, ice, mountains, forests or deserts. How do you rates your chances of survival after jumping?

I'm sure there are lots of other problems.

And for those learning to fly small airplane (with or without propellers). Can't you use or deploy parachute during emergency? This is a reasonable safety device and question.

Many glider pilots do wear a parachute. Not many have ever had to use it but it makes the seat more comfortable.

You can buy ballistic recovery parachute systems for light aircraft but they do add weight and cost. Weight increases drag and fuel consumption. Its your choice. They have saved a few lives.

PS: In 2013 a group of parachutists died in Belgium when their plane developed a problem at 3000m (about 9000 feet). Only three managed to get out of the plane before it crashed and their chutes opened too low to save them.
 
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