# Questions tagged [cruise]

The section of flight between the after takeoff climb and landing approach.

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### How to compute the mass flow rate for a turboprop at cruise given the static sea level value?

I am trying to obtain the mass flow rate of the Allison T56-A-15 used on the C130H at cruising altitude (so as to solve the Joule-Brayton cycle at cruising altitude). I know from "Turboshaft, ...
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### What is the effect of aspect ratio on cruise velocity?

Does the Aspect ratio affect the Maximum cruise velocity please? I was thinking it wouldn’t as Aspect ratio= b^2/S. If I wanted to go quicker I could just increase my span and decrease S?
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### Why do B787 Dreamliners more often fly at 42,975 ft rather than at 43,000, according to flightradar24?

The A350 and the B787 are the only passenger airliners that can be seen cruising as high as 43,000 ft on flightradar24 (with the exception of a B747 I once saw). However, the B787 is more often found ...
4k views

### Would an airliner climb higher late in the flight because of the consumed fuel (lighter airplane) to save more fuel?

Some people said airplanes would fly higher in the late period of each flight, because the fuel is consumed, and the airplane is lighter. Higher altitude and less dense air is enough to support the ...
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### Does the optimum LRC speed increase or decrease as the GW of the aircraft decreases during a long range flight?

I do not know what defines the optimum LRC speed for each aircraft, aeronautically speaking. I suspect it has something to do with optimum AoA but even then I am not sure if the LRC speed should ...
5k views

### Why are planes required to cruise at round flight levels only above 18000 ft of altitude?

AFAIK, planes flying at up to FL180 (18,000 ft pressure altitude) are allowed to fly at both round and semi-round altitudes (e.g. 15,000 ft or 15,500 ft). Planes flying above FL180 must fly at a round ...
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### How to most likely get a flight that will go above 40,000 ft?

I wonder if there are passenger flights that would reach cruise altitudes higher than 40,000 ft (i.e. reach 41,000 ft for instance) more likely than others. It also depends on the plane of course, but ...
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1 vote
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### Do most commercial jets cruise at constant altitude/speed?

The weight changes throughout, so this means aerodynamics efficiency changes to maintain constant speed and altitude. Is this how most commercial jets cruise?
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### Aircraft thrust calculation

I had a question regarding thrust calculation for an aircraft during cruise. For an aircraft flying at a constant cruise altitude and a constant Mach number (level unaccelerated flight), what exactly ...
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### Descent of Light attack aircraft to loiter altitude

How do Light Attack Aircraft (LAA) such as the Embraer Super Tucano descend from their cruise altitude to their loiter altitude to be on-station above ground troops? I want to know the way these ...
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### Optimizing the airplane for best cruising altitude and velocity

In the conceptual phase of the design, I am optimizing various entities of an airplane for the best cruising altitude and speed to reduce the cost, which also includes MTOW and fuel weight. Consider a ...
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### Relation between weight of the aircraft and mach number [closed]

Is there any formula that relates weight of the aircraft with mach number?
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### How is the Dash 8 Q400 so fast?

The Q400 has a cruise speed of 360kts, and on flightradar24 most Q400s that I looked at reached similar speeds during cruise. The ATR 72 has similar specifications yet only flies at 280kts. I'm ...
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### How much thrust is produced on an A320 at takeoff and during cruise?

Where can you get the drag polar of the A320 at cruise and TakeOff?
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### Based on this fuel flow chart, why isn't it more optimum to remain at an intermediate altitude rather than climbing?

I am having a bit of confusing as to why people say planes gets more efficient as they fly higher. Because on a typical long haul flight the Fuel Flow of the aircraft will obviously be much more that ...
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### Do pilots keep light in the cockpit during long night flights?

During long times of the cruise flight, is the internal light normally switched on or off inside the cockpit? Knowing it is generally dark in the night would make a smartphone-based night time logger ...
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### Relationship between wing aspect ratio and speed [duplicate]

For some reason, I cannot find a relatively straightforward source online which discusses the relationship of wing aspect ratio and how it affects speeds of an aircraft. Specifically, is there a ...
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### Why is the thrust-specific fuel consumption much worse for high bypass turbofans at cruise?

General Electric GE90 Takeoff: 0.278 lb/lbf/h (28.3 kg/kN/h) Cruise: 0.545 lb/lbf/h (55.6 kg/kN/h) Source: https://en.wikipedia.org/wiki/General_Electric_GE90#Specifications I assume this is typical ...
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### Why are heavy flaps better than just a bigger wing?

Flaps increase lift during landing and T/O. But when retracted, they do nothing. The space needed to stow the common fowler flaps can't be used for anything else - fuel or structure. Extended flaps ...
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### Cruise Mach Number less or more than Critical Mach Number

Do commercial airplanes cruise at Mach number higher than the critical Mach number? And what is the critical Mach number of airplanes like B777 or A330?
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### What is the main reason why cruise flight in the transition layer is prohibited?

What is the main reason why cruise flight in the transition layer is prohibited? For example if we have a separation of 1000 ft between transition altitude and transition level, why should we not ...
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1 vote
574 views

### How long is a climb leg in a step-climb cruise flight segment allowed to take, according to regulations (FAA/EASA)?

I am working on a trajectory optimisation program for commercial, large aircraft, in which I want to incorporate realistic air traffic control regulations. One of the constraints I want to incorporate ...
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### How do planes maintain constant speeds at cruise altitudes?

I'm a noob so pardon my ignorance. So my understanding is that as the plane gets lighter during the flight, its mass reduces therefore reducing the lift needed to maintain the altitude. At those ...
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### Tiny margin between VFR cruise and over Class C?

Our class C airspace at KRDU has a 4400 ceiling. If I fly Westbound above the airspace at VFR cruise, I'm expected to be at 4500. Since this is a tiny margin and I don't want to bust into the airspace ...
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### What is nominal n1 and fuel flow behavior during cruise climb?

For a commuter airliner (e.g. 737) performing a cruise climb (step climb) at a constant Mach, how should n1 and fuel flow behave? I know that fuel flow should decrease with altitude (air fuel ratio). ...
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### Does the Enroute Phase begin at a 30NM distance from the departure airport?

ICAO's Doc 8168 Volume II ("Aircraft Operations") states: Part III "Performance-Based Navigation Procedures" Section 1 "Underlying Principles" Chapter 1 "RNAV ...
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### Why cruise at 7000' in an A319?

I was on a flight from Philadelphia (KPHL) to Boston (KBOS), after some delay and some change of route due to weather, the captain announced that we will be cruising at 7000' due to delays in the area....
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### How do planes know what altitude they're cruising at?

I know that when planes enter the aerodome containing the airfield of destination, the ATIS will tell them an altimeter setting so the system knows how to calculate their altitude above their field; ...
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### Learn in-depth about airplane operations [closed]

Currently seeking a book or manual that teaches a civilian how a cargo aircraft operates and what it's pilots do, say a 787. Preferably a high-level overview at a per flight phase: Pre-flight: Flight ...
564 views

### Is there research suggesting that VFR cruise altitude rules improve safety?

In the United States, 14 CFR 91.159 prescribes cruising altitudes for level flight under VFR: (a) When operating below 18,000 feet MSL and (1) On a magnetic course of zero degrees ...
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### Why is the normal operating airspeed so much lower than the cruise speed in this table?

I need to work with the following table. I'm interested in vMO which I assume I can simply obtain from converting MMO to vMO through $M = v/ \sqrt{1.4 * 287 * T}$. (Is that correct?) However, I ...
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### Why would a plane drop 14.000 ft mid flight?

Just noticed American Airlines flight 221 dropped 14.000 ft mid flight today. Curious, what could have caused this? Here are the flight details.
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### Can airplane performance be increased by cruising "on step"?

Old timers swear aircraft performance can be increased by getting an aircraft "on step" similar to how boats are operated. They claimed a couple extra miles per hour (airspeed was in MPH then) were ...
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### What is the throttle setting of a piston aircraft during cruise?

I am learning to fly nowadays, I am sorry if this sounds like a dump question. What is the throttle setting of an aircraft during cruise flight? After stabilizing the flight after climb do i need to ...
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### What happens if full thrust is applied at cruise altitude for 5-10 minutes on a 787?

What happens when you apply full throttle to the engines of a Boeing 787 at cruise altitude for 5-10 minutes? Other than wasting fuel, what maximum speeds are reached? Does that pose any danger or ...
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1 vote
840 views

### What VFR cruising altitude should be flown to the west below 4500 feet?

This is similar question to this question, but different scenario. Let me describe the situation: I am at KDYL in class G airspace. Accroding to ATIS the clouds are at 4700 scattered. I am going to ...
300 views

### How do single GA pilots prevent boredom during long flights? [duplicate]

My question somehow relates to this question asking about how pilots cope with boredom, but now the scenario is not the typical airliner configuaration with two pilots, but with only one. I'm thinking ...
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### What throttle setting does an airliner use while cruising?

As a passenger, I have always felt like the engine are not kept at take-off thrust/full throttle a few (tens of) seconds after take-off, and so for obvious reasons as fuel efficiency, engine wear ...
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### What is the Fuel-Oxygen ratio for a large turbofan at cruise conditions?

What is the Fuel-Oxygen ratio (by mass) for a large turbofan at cruise conditions? In order to be concrete, I'll just pick an engine at random. I pick the GE90-115B. Okay it's not really random, it'...
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### The condition that wind would effect indicated airspeed [closed]

What is the one condition that wind does effects our indicated airspeed?
1 vote
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### How does change in airspeed affect pitching moment?

In aircraft with conventional elevator control, if I increase the speed, the horizontal tail sees higher velocity and hence higher lift. Does it mean that increasing airspeed creates nose down ...
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### How much does a Boeing 737 wing bend/deflect in cruise conditions?

As a part of my ongoing research of a structural joint analysis of a Boeing 737, I have been looking for sources where I may be able to find the bending/deflection data during cruise conditions. I ...
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### How much leverage do commerial pilots have on cruise speed?

If you fly frequently there are chances you have seen some delays in departure where you end up waiting in the aircraft sometimes for multiple hours. Almost every time that happened I remember the ...
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### What is a Cruise Captain?

I wonder what is a Cruise Captain, albeit I assume they are here to fly the cruise phase. Differences in responsibility / authority with a Captain? From training / certificate standpoint, what is ...
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### How can an altimetry system error during cruise (500 ft at 35000 ft high) cause an insufficient fuel situation?

So my boss gave me a question today as my daily quiz: Let's say an A321 is cruising on a 6-hour flight. It reaches FL350 30 minutes after take-off. After another 8 minutes there's a discrepancy ...
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### What is the order of Reynolds number inside the Compressor at cruise conditions?

I am doing a CFD study on a probe that will be installed inside a compressor of a civil aircraft for my final year project. I need to know the Reynolds number inside a compressor at cruise conditions. ...
1 vote
3k views

### What are the effects of headwind on ground speed and take off run? [closed]

I'm just making sure I got this right. For the take-off roll, having headwind is preferable, so there is a positive airspeed. For the en-route segment, a headwind is not ideal and increases time to ...
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### What would happen if thrust reversal is accidentally deployed during a flight? [duplicate]

Is it possible to deploy the thrust reversal, in the cruise phase of a flight? And, if they are accidentally deployed, what could be the possible consequences? As the cruise phase requires a lot of ...
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