Why do pilots say "rotate''? Take-off speeds explained

Take-off and landing are the two most critical aspects of any flight. Achieving a safe take-off is more than just acquiring ATC clearances and random taxiing down the runway. More often than not, pilots may have to take critical decisions, when speeding along the runway, whether to continue with the procedure or reject take-off. That's why it becomes absolutely essential to monitor the, what is called "take-off speeds" during this phase. These take-off speeds are  known as V1, Vr and V2, the critical speeds calculated by every pilot prior to take-off. Precise calculation of these speeds is of paramount importance as these serve as flags which would determine the pilot's response at that corresponding speed.

Inappropriate calculations of take-speeds or blatant disregarding of take off speeds can lead to possible lateral/longitudinal runway excursion, maximum brake energy exceedance, loss of control after the aircraft is airborne, brake fire or a tail-strike.

Before we get to why the pilots actually say "rotate", let's take a look at the other take-off speeds (in sequential order) :

Source

V1: Also known as " Decision speed". This is the speed beyond which take-off should not be aborted. The use of full reverse-thrust is not advised eitherVr: Also known as "rotation speed". This is the speed at which the pilot begins to apply control inputs " Pitching" the aircraft nose upwards. This effectively increases the angle of attack, thereby helping in achieving lift-off earlierV2: Once the aircraft has attained V2, take-off cannot be and should not be rejected. Should there be an engine failure, the aircraft will continue with the procedure even with one engine inoperative. In this scenario, the aircraft must be able to climb a minimum of 35 feet before the end of the runway(screen height)

Different jurisdictions may have differing definitions of V1.

The maximum speed in the take-off at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance-FAA(USA)

Critical engine failure recognition speed. This definition is not restrictive. An operator may adopt any other definition outlined in the aircraft flight manual (AFM) of TC type-approved aircraft as long as such definition does not compromise operational safety of the aircraftTransport Canada

Although V speeds are regulated by authorities, not all airlines are mandated by their SOPs to call out V2. It is to be noted that these speeds only apply to multi-engine aircrafts.Now that is established, let's see what really goes into calculating these speeds.

FACTORS AFFECTING V SPEEDS

Take-off weight: It's a no brainer. The rotation speed (Vr) is a function of the overall aircraft weight- fuel, souls in board and cargo. The higher the weight, higher is the Vr.Thrust and flap settings: Ideally, 100% of the available thrust is not used during take-off as this could lead to engine wear and tear. Flaps are generally extended during take-off to increase the lift quotient.Runway length, altitude and surface contamination: V1 will be lower on a shorter runway, especially on a wet runway as now the total runway length available is less. Airports located at higher altitudes mean aircrafts are now taking off at less denser air, which inadvertently impacts engine performance and lift.

Other environmental factors such as wind don't matter as much although high temperatures can have a significant impact on engine performance.

"Rotating" too early or a little too late can have consequences

In the event of a pilot rotating early, the aircraft hasn't reached the sufficient speed yet to be able to lift-off of the ground. This can lead to a "tail-strike" wherein the tail of the aircraft makes contact with the runway. Such an incident is not always fatal although it can prove to be costly.

Tailstrike of an A350

As you accelerate down the runway, the aircraft has an inbuilt tendency to lift-off anyway, owing to the aerodynamical design, hence a late rotation can affect V2 wherein the aircraft might not be able to clear the screen height of 35 ft before the runways ends.

In the event of an engine failure beyond V1,the take-off cannot be rejected and hence the take-off procedure is carried on.

Are these speeds the same for all aircrafts?

AircraftSingle engine Cessna 172 fully loaded Fully loaded B747MTOW1100 kg400, 000kgVr60knots160knotsDifferent aircrafts have different Vr speeds

Summary

Long story short, pilots say rotate as a verbal queue that the aircraft has reached its predetermined Vr and hence appropriate inputs can be applied to safely pitch the aircraft in a nose-up attitude to gain lift.

Definition

Acronym for "FULL AUTHORITY DIGITAL ENGINE CONTROL", is a digital computer system that controls all aspects of engine performance through inbuilt accessories such as the electronic engine controller (EEC) and electronic control unit (ECU) . FADECs have been manufactured for both piston engine and jet engines.

Description

As the very name implies, FADEC delegates the entire functioning of an engine to its inbuilt digital computers. That means the computers now have full authority over engine performance and there is no manual override available.Theoretically, it can only be installed on fuel-injected engines, thereby eliminating carburetors and carburetor heat.Engine performance parameters are maintained based on controlling the temperature and pressure. Mismanagement of fuel mixture control being one of the most common cause of engine failure, FADEC  helps bypassing it by maintaining appropriate fuel/air ratio on each cylinder within permissible limits.

Function

Current flight condition variables such as air density, engine pressure and temperature, throttle lever position etc are received by the EEC and analyzed upto 70 times per second. These inputs are processed to formulate critical data such as fuel flow, stator vane position, air bleed valve position which are then applied appropriately. Engine start from cold and restart is also managed by FADEC.

Safety

Since FADEC has the sole authority over engine performance, if it fails, the engine also fails. However, it may allow for manual override in which case it will considered solely as a EEC or ECU.With highly automated operations, safety is a concern and hence redundancy is provided in the form of 2 or more separate yet identical digital channels.That said, incorrectly installed engine control software can prove fatal as was the case of Airbus A400M that crashed in Spain on 9 May 2015 due to loss of thrust on 3 of its engines.

A400M CRASH IN SPAIN ( 9 MAY 2015)

How does it work in a civilian aircraft?

Prior to any flight, the flight crew enters all relevant data pertaining to the flight such as wind conditions, runway length, and cruise altitude into the Flight Management System ( FMS) . These variables are evaluated to produce power settings for various phases of the flight.

FLIGHT MANAGEMENT SYSTEM

Often times, during flight those variables may need to be altered to fly at optimum conditions. In any which case however, the FADEC is still in full authority and the crew cannot manually override it.

Advantages

In addition to providing efficient engine performance, it also allows the engine manufacturers to establish system limits and produce real-time engine health and management reportsReduces crew workload by providing digital assistance in engine monitoringProvides multiple redundant systems and saves weight

Technavio

Disadvantages

In the event of FADEC systems failing, the entire engine control is lost as there are no means of manual control availableComplex system when compared to hydromechanical, analogue or manual control systemsDuring emergencies, NON-FADEC engines may produce more thrust than what is rated as opposed to FADEC engines that will only work within specified limits.

Fortunately, most of the FADEC systems can be manually over-ridden today hence making it imperative that the flight crew is well aware of the location of the manual override in the cockpit. 

Why do airplanes go to graveyards? Yes, you heard that right. The massive tubes of metal that take to the skies, don't fly forever and there comes a time when even they have to make a final landing. So where do these aircrafts go after they are decommissioned from service?

Aircraft "boneyards" or graveyards

After retirement, these once giants of the skies retire to dusty parking lots known as "boneyards".The world's largest boneyard is the 209th Aerospace Maintenance and Regeneration Group (AMARG) at Davis-Monthan Air Force Base located close to Tucson, Arizona. Sprawling over a massive 2600 acres, this aircraft boneyard is filled with all decommissioned US aircrafts. 4400 jets worth billions against their original purchase price are stacked in this wide expanse.

A veritable Cold War armada of Boeing B-52s lies idle in the Sonora Desert sun at Davis-Monthan Air Force Base near Tucson, Ariz. (Paul Chesley/Getty Images)

Why scrap these beautiful pieces of engineering marvel?

Typically modern aircrafts are built to last as long as 25-30 years depending on their pressurisation cycles which determines their lifespan, although there is no set industrial norm for this.After a certain point of time, maintaining the airworthiness of an aircraft becomes a daunting task thereby prompting operators to either sell it off or scrap and recycle for further use.

With these aircrafts approaching the end of their operational life, specialized recycling firms come forward in what is known to be a very lucrative and established business with regards to aircraft spare parts and equipments.

The decision to dismantle an aircraft most often depends on whether the value of its parts and components is higher than that of the aircraft as a flying machine -says Mark Gregory, managing director of Air Salvage International, an aviation services firm based at the UK's Cotswolds Airport.

Apparently, even those aircrafts deemed to old to fly possess interiors that can fetch a fortune in the market.

Most of the value is in the engines, but there is an active market for all sorts of used parts and spares. It is often more interesting for an airline to replace a broken part with a used one, rather than repair it Says David Treitel , a former employee at Apollo Aviation Group based in Miami.

How are they scrapped?

Dismantling a jumbo jet is no easy task. For instance, a B747 has 6 million parts, 170 miles of wiring and 147,000 pounds of aluminum. Prior to breaking them down, the aircraft is flushed of all its possible hazardous and radioactive substances such as hydraulic fluids, batteries and de-icing liquids.Other valuable parts such as windshields, APUs, avionics, flight control systems can be refurbished and sold to be fitted on other aircrafts.Once the entire aircraft is stripped of all its valuables, and this includes precious metals like aluminium, titanium and stainless steel, the fuselage and wings are crushed for further recycling. About 85-90% of an aircraft is successfully recycled in this process.

Boneyard locations around the world

MOJAVE DESERT SOURCE

PINAL AIR PARK SOURCE

PHOENIX GOODYEAR AIRPORT SOURCE

SOUTHERN CALIFORNIA LOGISTICS AIRPORT SOURCE

ROSEWELL INTERNATIONAL AIR CENTRE SOURCE

Aircraft Fleet Recycling Association(AFRA)

SOURCE

The AFRA, established in 2006,is a leading global, non-profit trade group that oversees practices involved with the safe and environment-friendly procedure of aircraft scrapping.Boeing, Bombardier, Embraer, Rolls-Royce and many other top aircraft and engine manufacturers are members of the AFRA. Additionally, ARFA also offers support on disassembly, R and D and other services.  

Short snippet of a B747 scrapping

https://www.youtube.com/watch?v=qdKEC9kGhts

COVER: Pinterest

Every aircraft before taking to the skies have certain safety requirements it needs to adhere to. The same translates to aircraft lighting system as well.

Classification

Based on their application it is broadly divided into two, which is then sub-divided further.

Exterior lighting system: Provide illumination for operations such as landing at night, inspection of icing conditions, and safety from mid-air collision.Interior lighting system: Provide illumination for cockpit instruments and readings, cabin and all areas accessible to crew and passengers.

Additionally, there are certain special lights that also indicate the operational status of certain equipments.

Sub-classification

Exterior lights are further sub-divided into:

Position lights: Title 14 of the code of federal regulations stipulates requirements that an aircraft must adhere to prior to performing night operations. Consisting of one red, one green and one white light, the green light is always mounted at the extreme tip of the right wing while the red light is installed at the extreme tip of the left wing. The white light is usually installed on the vertical stabilizer at a strategic location from where it is clearly visible from the rear of the aircraft. Many aircrafts have single light units with a single lamp although nowadays it is more common to find light units with double lamps integrated onto the aircraft structure. LED lights are generally used on modern aircraft due to good visibility, high reliability, and low power consumption. Alternatively known as navigational light.

Anti-collision lights: Usually installed on the top of the fuselage or the tail in a location where it doesn't hamper the crew Visibility or illumination of the position lights. Aircrafts categorised under "large/heavy" use one on the top of the fuselage and one underneath it. They usually consist of one/two lights, rotating in an arc resulting in a flash rate between 40 and 100 cycles a minute. Also part of anti-collision lights, is a white strobe light, generally fitted at wing and tail extremities. This produces an extremely bright intermittent flash of white light that is highly visible.

Landing and taxiway lights: Landing lights are very powerful units used to illuminate runways during night landings. They are projected by a parabolic reflector at an angle that covers a maximum range of illumination. Typically installed in the centre-point of wings or integrated into the fuselage in small aircrafts while they can be spotted on the leading edge of the wing closer to the fuselage in bigger or more larger category aircrafts.

LANDING LIGHTS

Taxi lights, as opposed to landing lights, are not required to provide the same degree of illumination as their only function is to highlight the immediate vicinity when taxiing to the runway or towing away from the hangar. Strategically positioned at an oblique angle to the aircraft center-line, it illuminates the area immediately in front of the aircraft and to some right and left of it as well. Often times they are placed in the same area as the landing lights too. Smaller aircrafts may/may not have special taxi lights installed and hence rely on the intermittent use of landing lights while taxi-ing.

Wing Inspection lights: Most modern aircrafts are fitted with wing inspection lights and these aid the flight crew in the visual detection of icing/ice formation on the leading edges of wings, especially during night flying. Additionally, nacelle lights may also be installed in conjunction with wing inspection lights to illuminate areas such as engine cowl flaps and landing gear.

Interior lights

source

Interior lights are fitted inside the aircrafts to illuminate the cabin. Independent light system exist to allow personal use by passengers when cabin lights are dimmed. They are generally of a white and red setting.

Short snippet of aircraft lighting system

https://www.youtube.com/watch?v=0M1J9qQX1TQ

COVER: Airbus

source

According to statistical reports, most of the aviation fatalities occur during the critical phases of flight-take-off and landing. As much as they occur then, incidents are just as likely to happen during departure and arrival as well. Hence it becomes very imperative that the pilots are in constant communication with the ATC and ground control to avoid minor errors that could lead to grave fatalities on the runway.Here we'll talk about two of the most common, yet often mis-understood terms when it comes to runway incidents.

1.Runway incursion

source

Improper positioning of vehicles, ground service equipment and unauthorized personnel on any airport runway or any protected area at airside can lead to a runway incursion.

Classification

source

The FAA has classified runway incursions into 3 broad categories with further sub classifications based on their severity.

1.Operational incident: Improper separation between 2 or more aircrafts or between an aircraft and  ground obstacles-this generally takes place when minimum separation is not appropriately maintained. Clearing aircrafts on closed runways also lead to operational incidents.

2..Pilot deviation: Crossing runways en-route terminal gate without appropriate clearance from ATC is a clear violation of laws and is catergorized as human error.

3.Vehicle deviation: Presence of Unauthorized vehicles/personnel on active runways/taxiways or any area of the airside without ATC approval.

Sub-classification

Ample time and distance to avoid collision. Barely. avoid. collision. Significant. potential. for collision. Little or no risk of collision. Above scenarios are all classified as runway incursions, but with different severity codes. In each case the taxiing aircraft penetrated the runway safety area (hold position)

Based on their severity, it is further sub classified into 5 categories: (descending order of severity)

1.Accident: Collision resulting from an incursion

2.Category A: A serious incident that could have led to a collision but was safely averted.

3.Category B: In this case, the minimum separation is dangerously decreased further increasing the chance of a potential collision which also effectively impacts the time that could be taken for a corrective/evasive action.

4.Category C: This category witnesses an incident taking place that could have been timely avoided had minimum separation rules been followed correctly.

5.Category D: Any incident that qualifies to be a runway incursion but without any immediate safety consequences.

Modern airports are installed with Airport Surface Detection Equipment, MODEL X(ASDE-X) and the Airport Movement Area Safety System(AMASS) to alert ATC controllers of a possible runway incursion.

2.Runway excursion

source

Coming under the category of the most common type of landing accident, runway excursions accounted for about 80% of accidents (between 1995-2007) with fatalities, just a little ahead of runway incursion- according to Flight Safety Foundation. In simple terms, runway excursion is an inappropriate exit made by an aircraft from the runway.

A veer off or overrun off the runway surface-ICAO

Types of runway excursion

1.An aircraft failing to get airborne due to unsuccessful abortion of take-off, hence running out of active available runway. This could be due to miscalculation of take-off speeds, inappropriate weight and trim/power settings, aircraft system malfunction etc

2.A landing aircraft unable to stop before the end of the runway due to excessive touch-down speeds, missed threshold-crossing height, landing weight exceeding permissible values etc

3.A landing aircraft or one taking off may veer off course and depart the side of the runway. This could be due to aircraft systems malfunction, excessive wind velocity with cross-winds or loss of directional control due to aquaplaning

3.Runway undershoot

source

Interestingly enough, there can also be instances when an aircraft "undershoots" the runway. An aircraft is said to undershoot the runway when it lands at a point way before the designated one for landing.

On December 4,2020, a Spicejet flight, registered as VT-SLL and operating BLR-GAU sector, landed before the designated point and undershot the runway. Fortunately no passengers were hurt although this incident did damage quite a few lights on the runway. The pilots were subsequently grounded, pending further investigation.

source

COVER: European Cockpit Association

SpiceJet on Tuesday (August 17) announced it was transferring its cargo and logistics services on a slump sale basis to its subsidiary SpiceXpress and Logistics Private Limited. "The proposed transfer of the business to SpiceXpress will allow the new company to rapidly grow its innovative logistics platform and its unique fulfilment as a service business model," said Ajay Singh, Chairman and Managing Director, SpiceJet, in a statement.

SpiceXpress will also be able to raise capital independent of SpiceJet to fund this growth, he mentioned. He said he was confident that the performance of SpiceXpress as an independent entity will leverage and unlock significant value for SpiceJet and all its shareholders.

The airline's statement said: "The logistics business has been valued at INR 2,555.77 crore based on an independent valuation exercise carried out by the company and the purchase consideration for the same shall be discharged by SpiceXpress by the issuance of shares of SpiceXpress to SpiceJet, subject to all approvals as may be required." It is expected that SpiceXpress will operate as a separate entity upon transfer of business on or around October 1, 2021, it mentioned.

SpiceXpress

While SpiceXpress will operate as a separate entity, SpiceJet will continue to provide certain transportation services, ground and logistics support, management services, sharing and provisioning of resources etc. to SpiceXpress, it said.

SpiceJet said all related assets and liabilities, including, know-how, trademark, licenses, franchises, customer contracts and distribution network of cargo and logistics business would be transferred to SpiceXpress.

As per the quarterly results for the period ending June, the logistics arm continued with its strong growth story reporting yet another profitable quarter with a net profit of INR 30 crore. "The revenue increased by a whopping 285% to INR 473 crore for the reported quarter as compared to INR 166 crore in the same quarter last year," the airline's statement noted.

The logistics arm has a network that spans over 68 domestic and over 110 international destinations including the US, Europe and Africa, it mentioned.