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Permalink Reply by Dr. Krishna Kumari Challa on May 29, 2025 at 9:27am

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What´s a RAT? RAM AIR TURBINE!

Permalink Reply by Dr. Krishna Kumari Challa on June 13, 2025 at 8:30am

Well, people are asking me questions about yesterday’s tragedy. I am not an expert and moreover investigations are going on. At present we can only speculate.

Generally speaking, however, when you investigate air crashes, they often involve a chain of problems. One thing happens, then a number of events follow from that. So it might not be one cause here.

This crash occurred shortly after takeoff. While flying is statistically the safest form of transport, the takeoff and landing phases are generally considered the most critical. This is because aircraft operate closer to the ground, with less time and altitude to respond to technical issues or sudden changes. Although not inherently dangerous, these phases carry a higher risk of incidents compared to cruising at altitude.

Other pilots and ex-pilots are speculating these things after analysing the video footages:

1. Runway length and heat: Radar data indicates the pilots may not have used the full length of the runway. On a hot day in Ahmedabad, where temperatures reached 40°C (104°F), a heavy aircraft requires more distance to reach liftoff speed due to reduced air density. If a plane tries to lift off too early without enough speed or lift, it could crash into a nearby obstacle or fail to get airborne. Unverified data suggests Flight 171 may have used as little as 1,900 meters of runway, below the 2,500 meters generally recommended under those conditions. The Dreamliner is a heavy jet, used for long international flights, carrying many passengers and fuel, so it can struggle if something's off.                        

   Some individuals on PPRuNe, a pilot’s forum, suggested the shortened runway was on the lower threshold of what may have been advisable.

   This practice is often used by pilots to avoid traffic jams and air-traffic control delays, and is permitted if deemed safe.

   Planes get less lift on a hot day due to lower air density, and therefore they need to go faster to get as much lift as on a cooler day.

   Flight AI171 took off in 40°C heat in the early afternoon sunshine of Gujarat.

   A plane struggling with insufficient speed or lift could hit a low obstacle or fail to overcome its inertia if lifting off early.

                                     But some reports are saying the pilots have used the entire runway, so we don't know the truth yet.

The SOS sent ( Mayday, Mayday, Mayday) indicates something definitely went wrong.

2. Multiple aviation analysts think the aircraft's wing flaps were not correctly deployed at the time of takeoff. The flaps, which are essential for creating lift at low speeds, appeared to remain retracted, based on early video analysis.

It looked like the jet struggled to maintain lift. Some pilots have speculated that the flaps may not have been set to the takeoff position. Historically, there have been crashes when flaps weren't properly configured.

The footage suggested the flaps were not extended, and “the aircraft would not have been able to maintain flight" under those conditions. The landing gear remained down, further impairing the aircraft's aerodynamics.

Captain Summeet Sabharwal, who was commanding the flight, had more than 8,200 hours of flying experience. Experts say that level of experience makes it less likely the flaps or gear configuration were overlooked due to a procedural mistake, but do not rule such catastrophic pilot error out entirely.

It may not have been set properly. If that is the case, that is definitely human error - flap settings are a crucial part of the pre-takeoff checklist.

That's why pilots use checklists and double verification to ensure flap settings are correct before takeoff. It's an essential safety step, especially on heavy planes like the Dreamliner.

Experts have suggested that video footage of the flight’s final seconds showed that its wing flaps were incorrectly set for a standard take-off climb.

Flaps affect an aircraft’s aerodynamics by changing the shape of the wing, and play a crucial role in getting it airborne. Yet based on some interpretations of the video evidence they were fully retracted, a position in which they would provide minimal lift.

The aircraft’s landing gear also remained deployed throughout the short flight, when on a 787 the wheels are normally withdrawn as soon as they leave the runway.

One possibility is that the landing gear became stuck and that the pilots responded by partially retracting the flaps to reduce drag and maintain the climb. If the adjustment was overdone the plane would lose lift and begin to descend.

At some point the 787’s wing would have stalled – the term for when the airflow is separated from the wing’s surface – through the combination of insufficient lift and excessive drag.

A more straightforward explanation may be that the flaps themselves malfunctioned, failing to respond to inputs from the cockpit.

The Boeing 787 has experienced flap issues in the past

However, some pilots are saying we cannot say anything for sure about the wing flaps as the pics taken from a distance are not very clear.

3. Bird strikes can be very challenging. Especially if an engine ingests birds and fails, as happened in the [2009] US Airways Hudson River landing. The most likely cause of a double engine failure at low altitude would be a bird strike. Because the altitude was so low, the pilot would have had very little time to do an emergency landing. The aircraft appeared to lose power "short of taking the gear up," which can happen "only in case the engine loses power or the aircraft stops developing lift. Ahmedabad airport is known for its bird strike hazard. According to The Telegraph, it had the second-highest number of reported bird strikes in India in 2023, despite operating significantly fewer flights than major hubs like Indira Gandhi International Airport in Delhi.

But, we didn't see bird flocks in the picture and moreover, we  didn't see any smoke or fire scenarios in the engines to confirm this.

4. Landing Gear Remained Deployed: A recurring point in expert analysis is the plane's failure to retract its landing gear. Typically, pilots raise the gear within seconds of a positive rate of climb. In this case, the gear was still extended when the aircraft went down. There are two things that are needed for an aircraft take-off. One is adequate airspeed and the other one is a rate of climb. And that plane had neither. It could have been he [the pilot] just didn't have time, or it could be that perhaps he thought he could control it, go round again and land or even land straight ahead. So that remains, if you like, a mystery.

Some pilots are saying when the two pilots in the cockpit were busy tackling an emergency situation, the landing gear  retraction would be the last thing on their mind.

5. The pilots had very little time, just about 20 seconds, which was just enough to understand what the problem was, and not enough time to react and correct it. Moreover, the plane was still at a very low altitude, that height was not enough as there was no space to recover. They just didn't have a chance. Feel very sad about it. 

That is why they say taking off and landing are the most dangerous and difficult parts of flying. Taking off more so because you have lots of fuel then to cover the entire journey and if something unusual happens that would be like a huge bomb that could explode!

Gear retraction and flap extension are both critical for lift and speed. If the flaps malfunctioned, or if the pilot was unaware they hadn't extended, it becomes very difficult to control the aircraft safely.

6. Technical error or engine failure

A significant loss of thrust, as appears to be indicated in the stricken plane’s mayday call, could have resulted from a number of causes.

A wholesale engine failure – especially of the “uncontained” variety, where a turbine disintegrates due to failed bearings or blades – can be catastrophic, flinging out debris that shatters the engine casing and penetrates the fuselage.

However, evidence of such an event should have been visible in the video footage, which showed no obvious signs of engine problems other than the plane’s struggle to gain altitude.

Engine failure could also have resulted from a less dramatic issue, such as a fuel-related problem.

Given that the plane had been prepared for a long-haul flight – and the size of the fireball when it came down – it could hardly have been out of kerosene. But fuel contamination or mis-fuelling of some kind could have led the turbines to underperform.

Technical or engineering issues – such a fuel pump failure or malfunction of engine controls – could also have conceivably led to the disaster.

It also means that the exact fault behind the loss of power, if that proves to have been the reason for the crash, may be difficult to ascertain, although readings from the plane’s black box flight data recorder, once recovered, should provide vital information.

If the plane is found to have been brought down by a fundamental flaw, then the entire fleet could face grounding, though with the model in service for so long without incident a maintenance-related glitch may be more likely than a manufacturing or design error.

It appears from the video, there is a cloud of dust just after take-off . 

The aircraft then seems to lose power and the pilot appears to increase its angle of attack to try and stay airborne for longer.

The aircraft could fly perfectly well on one engine. But without any power, the pilot has no choice but to do an emergency landing.

It is not certain, but it appears as though the cloud of dust could be from the engines as they both fail.

And now another video added above  gives  another evidence ; the Ram Air Turbine (RAT) deployed—something that only happens in the event of significant power loss. This changes everything. The RAT deployment means,  the very real possibility that this was a dual engine failure scenario.

7. Overloading

It is possible the cause of the crash was that it was too heavy to take-off.

The weather, again, is a factor in this as it dictates how much ground velocity a plane needs to generate enough lift to get airborne.

However, this is checked by the airline ahead of take-off and experts say unless there was egregious oversight or error, it is improbable as a root cause.

“It is very unlikely the plane was overweight or carrying too much fuel – there are careful checks on this,

After the investigations are completed, we will get the full picture of this tragedy. 

Until then... respect the correct process - Investigators need to work without external pressures to ensure accurate findings. Respecting this process maintains integrity and supports the many people who are currently experiencing unimaginable grief.

And the pilots might  have done everything possible - the nose went up before crash landing which is a sure sign of this - in the very little time they had but sometimes that wouldn't be enough when the situation goes completely out of your control. You just pay with your life despite everything. That is the real tragedy.

One in a million chance becoming a reality. A situation where you just throw your hands up and say, " I surrender to what is about to happen!" Nobody wants to be in such a situation where control is not in their hands.

Permalink Reply by Dr. Krishna Kumari Challa on June 13, 2025 at 10:41am

Lift vs. Power – What Really Happened to AI171?

Permalink Reply by Dr. Krishna Kumari Challa on Monday

Planes Can Fly Without Their Engines, Here's How

Permalink Reply by Dr. Krishna Kumari Challa yesterday

What could have caused the Air India crash? An expert examines the proposed failure scenarios

Author: Ali Elham

The recent crash of an Air India Boeing 787 Dreamliner in Ahmedabad has prompted widespread discussion about potential causes. As an expert with a background in aircraft design, I would not attempt to speculate on the cause of the incident. We should wait for the crash investigators to carry out a rigorous analysis.

Instead, I will explain the various flight scenarios currently being discussed in the public domain, and explore what each of them implies from the perspective of aircraft design and performance.

Understanding how such factors interact with aircraft systems and flight performance can shed light on how modern aircraft are designed to handle rare but critical situations.

Loss of engine thrust

Modern commercial aircraft are designed to safely continue takeoff and climb with one engine not operating. This is a fundamental certification requirement, particularly for twin-engine aircraft. It ensures that the loss of a single engine, even during the critical takeoff phase, should not result in a catastrophic failure.

However, the loss of both engines is an extremely serious scenario.

A notable case of dual engine failure occurred in 2001 on Air Transat Flight 236, which was traveling from Toronto, Canada, to Lisbon in Portugal. The Airbus A330 aircraft lost both engines over the Atlantic Ocean due to a fuel leak, but managed to glide approximately 75 miles (120km) before safely landing at Lajes Air Base in the Azores. This was possible because the aircraft had sufficient altitude and airspeed at the time of its total engine failure.

However, takeoff and landing are considered the most critical phases of flight because the aircraft is close to the ground, giving pilots limited time and altitude to respond to failures. At low speed and altitude, the aircraft may also lack the necessary energy (in terms of both airspeed and height) to glide a meaningful distance.

Bird strikes can also cause engine failure, as seen in the case of US Airways Flight 1549, an Airbus A320 that struck a flock of birds shortly after take off from New York's LaGuardia Airport on January 15, 2009. Both engines failed and, due to the aircraft's low altitude and limited speed, the pilots determined that returning to the airport was not feasible.

Instead, pilot Chesley "Sully" Sullenberger and co-pilot Jeffrey Skiles executed a successful emergency water landing on the Hudson River, resulting in the survival of all onboard. As such, the incident became known as the "miracle on the Hudson."

These examples highlight how altitude, speed and pilot decision-making, along with robust aircraft design, play a critical role in the outcome of rare but severe engine failure events.

Landing gear not retracted

During a normal takeoff procedure, the landing gear—the sets of wheels under a plane that support it on the ground—is retracted within seconds after liftoff, once the aircraft has safely left the ground.

Extended landing gear produces significant aerodynamic drag. So, during the initial climb when the aircraft requires maximum thrust to gain altitude, eliminating this drag by retracting the landing gear is highly beneficial for both climb performance and fuel efficiency.

However, commercial aircraft are designed to remain controllable and flyable even if the landing gear fails to retract. In such cases, the aircraft should still be able to perform a "go-around" before safely landing again, assuming no other critical failures have occurred.

That said, a scenario involving both loss of engine thrust and non-retracted landing gear can severely degrade glide performance. The additional drag from the extended gear reduces the aircraft's lift-to-drag ratio, an indication of the aerodynamic efficiency of the airplane.

The extended landing gear might limit the distance it can glide and increase its descent rate—which is especially critical when altitude is limited.

Flaps retracted prematurely

An aircraft's ability to generate lift depends on several factors, including wing area, airspeed, altitude, and the "lift coefficient"—a number that describes how effectively a wing or other surface generates lift under specific flight conditions. The lift coefficient is largely influenced by the wing's geometry, particularly its curvature (called camber).

During takeoff and landing, the aircraft operates at relatively low speeds where the wings alone may not generate enough lift. To compensate, high-lift devices such as flaps are deployed. These devices are usually mounted on the wings' trailing edges and, when extended, increase each wing's curvature and surface area, thereby raising the lift coefficient and allowing the aircraft to remain airborne at lower speeds.

However, deploying flaps also increases aerodynamic drag. For this reason, once the aircraft accelerates and reaches a safe climb speed, the flaps are gradually retracted to reduce drag and improve fuel efficiency.

If the flaps are retracted too early, before the aircraft has reached sufficient speed, there can be a sudden loss of lift. This may result in a stall or insufficient climb performance.

This situation becomes even more critical if it occurs in combination with other issues, such as extended landing gear (which increases drag) or a loss of engine thrust, as the combined aerodynamic penalties may prevent the aircraft from maintaining

Conclusion

Over the years, numerous improvements in aircraft design, maintenance and operational procedures have resulted from crash investigations. Each incident, especially a fatal one such as the Air India Boeing 787 crash, offers valuable lessons that can drive further enhancements in aviation safety.

The fact that both the aircraft's flight data recorder and cockpit voice recorder (sometimes referred to as the "black boxes") have now been recovered offers hope that the precise cause of this crash will be identified.

Whatever is ultimately determined to be the cause—technical failure, human error, or a combination of both—there will be lessons to be learned. Every event highlights areas where systems, procedures or training can be strengthened to make aviation even safer in the future.

This article is republished from THE CONVERSATION under a Creative Commons license. Read the original article.