# Tag Info

17

There's a lot of nonsense being banded about regarding this flight. First up, we are not talking about sustained, powered climb rates. If you're travelling at Mach 0.85 and pull up vertically, in theory (if your plane didn't break) you'd climb at an initial rate of nearly Mach 0.85 (your original speed minus the airspeed loss when pulling up).... That's near ...

16

The energy variometer gives the rate change of total energy of the aircraft expressed in vertical knots. A traditional variometer gives the vertical speed of the aircraft derived from the change in barometric pressure. This is very useful for gliding, especially when looking for thermals that lift you up. The problem with ordinary variometers is that they ...

14

Large commercial jets operate within a much wider range of weights than most GA aircraft do, and since Vy varies with weight, it wouldn't make sense to publish "a" single Vy speed for them. The crew can get a best rate or best angle of climb speed from the FMC (which "knows" the current weight of the aircraft, based on current fuel & an entered Zero Fuel ...

14

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

Vertical speed, as measured by the Vertical Speed Indicator (VSI) should be measured entirely by the changing air-pressure at the static port, and should be completely unrelated to airspeed and ground speed. The static port is a small hole, (about the size of a large needle or tiny nail) in the side of the airplane, with a pressure-sensor inside. As that ...

12

Does normal laws apply when the aircraft nose is vertically down? Yes, always. Physics doesn't care much about the aircraft's attitude and cannot be switched into different modes. While the nose points straight down, a stall is hard to achieve since no lift is needed - the weight is balanced by drag and inertia. However, when you pull abruptly and start to ...

11

In general terms, the higher you are the better your fuel efficiency, so you will want to climb quickly and then stay as high as you can until you need to start your descent in order to land. For jets, a common way to approximate your top of descent is by using the "3:1 rule" where you take your desired altitude loss in thousands of feet and multiply it by ...

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 ...

9

This is certainly not a comprehensive answer but can get you started. I’m assuming fixed wing non-VTOL aircraft. A low (forward) speed touchdown, all other things being as close to nominal as possible in that scenario, translates in all likelihood to a steeper than normal landing and can be associated with loss of sufficient lift or even stall and can ...

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

(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. ...

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 ...

6

Airplanes certificated under FAR Part 25 (Transport Category Airplanes) must meet far more complex and regulated takeoff performance criteria than can be reduced to a (light aircraft) Vy or Vx (Vyse or Vxse) speed. If you're taking off in a Cessna 310 and interested in gaining altitude as quickly as possible (rate) then having a published Vy speed (which ...

5

Absolutely. Stalls occur when the critical angle of attack is exceeded, plain and simple. While it's easy to see this when the aircrafts nose is really high above the horizon it can actually occur at any attitude, even nose down or straight and level. Angle of attack is determined from the oncoming relative wind and the reference line of the wing (the ...

5

The Mesa E175 that had an emergency descent about a year ago peaked around 7000 fpm, in total taking 6 minutes to descend from FL340 to 10,000 ft. (flightaware.com) In light of the comments above about MMO/VMO and lift/drag limiting descent rates, you can accelerate descents by banking the aircraft into a turn. This allows you to increase angle of attack, ...

5

I can't answer for to 40,000 feet (FL400—Flight Level 400—in pilot parlance), nor to an A320 or B737. I can answer for a piston engine airplane with retractable landing gear at FL250, though. As a private pilot, I frequently fly our Mooney 252 (M20K) at FL250. I did an emergency descent drill, running through the procedures to initiate a maximum-rate safe ...

5

Your math looks right to me. If an airplane has the statistics that you listed there, then it will accelerate upwards at $16.48\ \mathrm{m}/\mathrm{s}^2$, as you calculated. The occupants will experience about 3 g's of proper acceleration (1 g from gravity, and about 2 g's from the acceleration). But here's what would actually happen, in context. To start,...

5

The 787 was not designed to perform such a maneuver. Any jet airliner could do this. What you need for such a steep climb is a good thrust to weight ratio (or enough excess speed to bleed off during the maneuver). A passenger twin-jet is designed such that it can still climb with at least 2.4% climb gradient after a single engine failure during a takeoff at ...

4

Concorde did something similar: it would take off from London at sunset and then fly West faster than the Earth's rotation, so you would get a sunrise in the West on board. This capability was also used for solar eclipse flights. While a solar eclipse lasts no more than 8 minutes on the ground, Concorde was able to stay in the Moon's shadow for 74 minutes.

4

The 787 (and other commercial aircraft) are built to carry large loads, whether lots of cargo, or lots of passengers and bags. So, when empty, their performance is much better. If it can do a normal takeoff when full, then it can do a rocket-like takeoff when empty. The near vertical takeoff is, indirectly, a demonstration of how much power it has when ...

3

I'm surprised no-one has attempted to answer this question, as it is mostly a pilot's daily job to guess a pitch change that would give a certain rate of climb. :-) This will not be a technical answer, but I suspect some of my attempts at controlling the rate can be ported to a PID algorithm. Keeping math aside, if you draw the lift-drag-thrust-weight ...

3

You need ground speed not TAS. GS is affected by the head- or tail-wind components. Assuming in your example GS is 75 knots, then just check how long it takes to change altitude. 11,200 ft at 1,250 ft/min takes 8.96 minutes, or 0.1493 hours. At a speed of 75 knots, that's 11.2 NM. \frac{\text{altitude change (ft)}}{\text{rate of climb (ft/min)}\cdot60}\...

3

Yes. It appears to be the case for "steam gauges". At least for a traditional vertical speed indicator. It's a great question and not one I had considered before. At first glance, I suspected you may be right, though I don't ever remember actually learning that. To prove the theory, one pilot apparently took his airplane with a traditional ...

3

A variometer is a similar instrument to as a VSI (Vertical Speed Indicator) or VVI (vertical velocity indicator). They are very important in gliders (what it appears the picture shows), as it indicates the presence of rising or sinking air. In powered flight, they are used to indicate level flight (or set a desired descent rate). Gliders utilize a ...

3

In speed mode, the autothrust varies engine thrust to maintain the pilot selected or the FMGC (Flight management guidance computer) calculated speed. In V/S mode, the priority is the selected vertical speed. If the vertical speed is high to the point, the set speed cannot be maintained with the set thrust, the aircraft will decelerate or accelerate depending ...

2

In "full up" FMC/VNAV/Autothrottle airplanes, Level Change tends to be an "all or nothing" option for power: full climb power to go up, and flight idle to come down (with pitch holding the commanded speed in both cases). With Vertical Speed, the pitch holds your climb rate constant, and the throttles vary to hold your airspeed. With a sufficiently large V/...

2

Well they do of sorts. But your pilot friend is right, they are not tabulated for a transport category aircraft like is done for a Part 23 aircraft. Due to the large payloads, CG ranges and configurations, the best rate of climb speed must be computed for each situation. There is no one published Vy for a large transport category airplane. Incidentally ...

2

It describes what the velocity vector of the aircraft centre of gravity is in relation to the surface of the earth. Ground speed is the 2-D projection of your speed on the ground, climb speed is the vertical component. Both ground speed and climb speed are very useful parameters as such: ground speed to figure out when the aircraft arrives, climb speed to ...

2

First, you need thrust-to-weight¹ ratio more than 1, so the device can maintain flight. You should be able to find data about how much thrust (lift in case of rotors; it's the same thing) they can produce and how much power from the engine it takes for some existing propellers and rotors. The efficiency, that is thrust-to-power ratio, generally increases ...

2

The best propeller driven vertical take-off and landing craft would be a helicopter, actually. Yes a duct around a propeller increases thrust, but upsizing a propeller creates way more thrust from the available power. Propeller thrust has scaling effects with size due to different Reynold numbers, data does not scale up well. Best way forward from where you ...

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