# Tag Info

25

Very frequent. Modern airliners are certainly fairly slippery, but it's not so much that they're super-gliders that we can't wrestle down onto the ground. It's more a function of busy airspace than a property of the aircraft. When you remove power from any aircraft, it's going to descend - the only question is the rate. I promise you that if you found ...

25

Airline pilots certainly do use gear/flaps/spoilers to descend more quickly if needed. However, SOP typically requires an approach to be stable upon reaching a certain altitude on the approach. This means having speed and airplane configuration set for landing, and being lined up with the runway and on the glideslope. Unstable approaches are more likely to ...

17

Whether there are any formal policies for when to request descent will depend on the airline. However, I doubt formal procedures are established, since it should be pretty obvious to pilots when to request descent. From a controller point of view, I will expect you to request descent when you are ready for it - so a minute or so before reaching your top of ...

16

There are a few possibilities, there's no way to know which is correct without more information: There could have been an emergency on board. If someone is showing signs of a serious illness pilots will get the plane on the ground in a hurry to get the person medical attention as soon as they can. Or there could have been an issue with the airplane or a ...

16

Glide ratio is the ratio of the distance a glider can travel horizontally to the altitude lost in transit. For instance, if a glider can travel 40 miles horizontally while losing one mile of altitude, the glide ratio is 40:1 (typical for a medium-high performance glider). The best glide ratio or maximum glide ratio is simply the best ratio a glider can ...

16

I actually got asked a similar question on a checkride two weeks ago. Right after I was asked to demonstrate an emergency descent through a hole. I heard the talk about the advantages of the substantially increased drag of the Fowler flap, and was quizzed about impact of drag with higher speeds. Meanwhile I extended full flaps, and slowed the plane. ...

14

If the pilot reduces the airspeed while he increases the rate of descent, you will not notice any change in pitch attitude when the aircraft descends. With jets you should be able to hear a change in engine pitch when thrust is reduced. Turboprops run their engines at constant speed, and a reduction in power here means a reduction in propeller pitch. This ...

13

Descent planning for jets can get a little tricky at times, and you have pointed out some of the things to look at when deciding when to start down (assuming that ATC gives you the option to choose your own top of descent). The descent point is dependant on your aircraft and how much drag there is at your descent speed. Anything that adds more drag allows ...

13

Basically, it's a combination of historical significance, passenger comfort, and ease of mental calculation. Historically, before aircraft were pressurized a rapid descent would be uncomfortable for passengers. At the speeds typically flown, a 300ft/min descent was deemed to be comfortable enough for the typical passenger. Many aircraft had a cruising ...

13

For a comfortable decent you generally want to come down at 500 Ft/Min on the Vertical speed indicator. The 152 is doing about 95Kts over the ground (assuming no wind). So you are covering about 1.5 miles a minute to round it off. So you need to drop 5000 ft on your approach to the area. At a comfortable rate that will take about 10 minutes. In that time, ...

13

There are two reasons I can think of off the bat: Its possible the controller asked them to hold a slow speed due to increased traffic ahead. The brakes may have been deployed to match the speed requested. I have heard this called on occasion over the radio in the terminal area I fly. The controller cleared them for a steeper decent than usual this would ...

12

Normal descent rates will vary by operator and by airframe, but in general they follow this logic: Power at flight idle, Airspeed at or near max mach number or max KIAS, Spoilers stowed. Generally they wont push airspeed right up to the limits and incorporate a small margin, but this is general idea. This is the most efficient descent because it means you ...

12

FLC mode maintains airspeed during a climb or descent, while VS mode maintains a specific vertical speed. Often air traffic controllers will request that you "maintain 250 knots in the descent" or something to that effect, which is much easier to achieve when using Flight Level Change. As another answer points out, by maintaining airspeed, climbs are made ...

12

You haven't provided everything possible to really ascertain the issue noted, but based on what you have I've noticed the following things: You'll find most 737s at 240-250 KIAS passing through 10000 feet, rather than the 220 knots that you were going at (while 220 KIAS is above minimum clean speed at normal landing weights, it's still slower than most) ...

12

If the pilot commands a certain glide path angle, any change in airspeed will also change vertical speed, because both are connected by the glide path angle $\gamma$. Note that the vertical speed is air speed$\cdot\sin\gamma$. Climbing or descending makes no difference; only the sign of $\gamma$ changes (positive $\gamma$ means the aircraft climbs). Also ...

12

I looked up the flight on Flightradar24.com. The descent starts at 16:10 UTC and ends at 16:29 UTC, going from 38.000 feet to 24.000 feet. So, the aircraft descended 14.000 feet in 19 minutes. 14.000 divided by 19 makes roughly 750 feet per minute, which is a relatively normal descent rate for airliners. The cause for this is probably an ATC instruction. ...

12

Approaches into Schiphol are usually vectored by ATC during the day (see below for night operations). This means the controllers are giving instructions to pilots depending on the current traffic, which makes it hard to say when exactly planes will overfly Egmond aan Zee. If the Polderbaan (runway 18R/36L) is used for landing from the North (18R), planes ...

11

Those are spoilers...not speed brakes. They do increase drag, but their primary function is that they kill lift. They allow the aircraft to lose altitude rapidly without pointing the nose downhill and picking up speed. You will also see them deploy upon touch down. At high speeds they increase drag and thereby aid in deceleration, but again they kill ...

10

You can descend down to 100ft above TDZE if you have any ALS in sight. You need an ALS with red lights (ALSF I & II) to go below that. Red terminating bars/red side row bars help you find the threshold. Think of an ALS with red lights as being in the same category as Runway/lights/markings, Threashold/lights/markings, Touchdown Zone/lights/markings, ...

10

For ATC planning of jet transport aircraft, 3NM per 1000 ft, plus 10 NM for deceleration is used as a rule of thumb. $$FL300=3\times30+10=100NM$$ Most of the 10NM for deceleration will be consumed at around FL100. Weight should not change the descent distance a lot, it mainly affects the speed. The lighter the slower.

10

Just MHO: Vertical speed should never be used when climbing because you could stall if insufficient power is added for the requested climb rate. Using FLC when climbing guarantees you maintain the best airspeed (best rate or best angle, depending on the situation) On the other hand, when descending I always use VS mode because it gets you down to the ...

10

Descent is a matter of managing the aircraft's energy budget. To descend, the aircraft must shed all its potential, and big part of its kinetic energy. Pilots reduce engine power to minimum to stop adding energy, but the energy the plane already has is still only dissipated by drag. The angle at which the aircraft can descend without accelerating is equal ...

9

They are different modes that control aircraft pitch in different ways, and as a pilot you select what you want based on your current requirements. Note that the modes even behave differently depending on the aircraft / autopilot, so referring to the actual aircraft/autopilot documentation is essential. Many autopilots don't even have a Flight Level Change ...

9

The statement is only true if you fly at a speed below the best glide speed. For simplicity, let's look at a glider: Below you see the plot of the L/D ratio over speed of the DG-1000 two-seater glider: Glide ratio over speed diagram for three different wing loadings (source). If we just look at the lowest wing loading (leftmost curve), the best L/D can be ...

9

(wikimedia.org) Part of a Boeing 747-400's autopilot control panel. Maximum rate climbs and descents are achieved by using a speed climb/descent mode, where the pitch (nose up/down) controls a selected speed. The button FLCH (flight level change) activates such mode (shown above). Each manufacturer has its own name for it, but it's the same functionality. ...

9

To address your questions: First, slips are perfectly reasonable for controlling descents. In some aircraft, for example, many Cessna 172s, are placarded warning against extended slips with full flaps. In the 172 case, there may be some buffeting. Years ago, slips were emphasized more than they are today. Of course there were more primary aircraft without ...

8

Because the Top of Descent (TOD) is calculated in flight based on current weather data, STAR/Transition assigned, directs received during the cruise portion of the flight, vectors received taking you off your planned route, etc.. The FMC does the calculation for you with higher precision in flight. For regular ops, ATC can use the rule of thumb 10.000ft / ...

8

However, I don't understand how the lowest sink rate you can get isn't the same as the shallowest angle you can glide at. Look at a Polar Curve: The lowest sink rate you can get is the maximum value of the curve, as illustrated in this image taken from the wiki article above: The shallowest angle you can glide at is given by the tangent to the curve that ...

8

In a rapid depressurization, you'd typically descend at MMO and transition to VMO until reaching your level-off altitude. This is accomplished with the speedbrakes extended. What vertical speed you'd get is unknown; essentially you take whatever rate this procedure gives you. Initially, it might be 6000+ FPM, after transition to VMO, maybe a little less than ...

8

No, both would reach the ground at the same time, although the one with the higher airspeed would go farther before hitting the ground, assuming atmospheric conditions are invariant. On the other hand, if both aircraft have the same flight path angle, the one with the higher airspeed would have a higher sink rate.

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