PK661: These Are the Reasons Behind the Crash [Analysis]

Pakistan International Airline’s flight PK661 operating from Chitral to Islamabad on an ATR 42-500 with 42 passengers and 5 crew members crashed yesterday near Havelian, some 80KM north of Benazir Bhutto International Airport.

No one survived the crash.

While it is too early to list down the exact reasons behind the crash, we will try to analyze available information and try to come up with possible reasons for the crash of flight PK661.

What We Know About PK661 Aircraft?

ATR 42-500 is one of the most recent versions of ATR aircraft. Its first delivery was made in 1995 while the flight in question, PK661 with Registration AP-BHO, was delivered to PIA in May 2007.

ATR 42-500 comes with six-bladed propellers powered by PW127E engines rated at 2,400 shp (1,800 kW) for improved hot and high performance and increased cruise speed.

ATR 42-500 engines are certified to be safe, strong and solid performer in a variety of conditions.

It had flown 18,740 hours before it crashed yesterday.

Crashed aircraft details are as following:

  • Aircraft Type: ATR 42-500
  • Manufacturer: ATR
  • Registration: AP-BHO
  • Certificate of Registration Number: 751
  • Registration Date: May 18, 2007
  • Operator/Owner: Pakistan International Airlines (PIA)
  • Construction Number: 663
  • Year Built: 2007
  • First Flight: May 3, 2007
  • Test Flight Registration: F-WWLU
  • Delivery Date: May 14, 2007
  • Aircraft Name: Hasanabdal

Weather Conditions

Weather conditions at the time of crash in the area were quite normal.

Below are weather values for Havelian at the time of the crash:

  • Time of incident: 4:10PM
  • Temperature: 23.0 °C
  • Dew Point: 10.0 °C
  • Humidity: 44%
  • Air Pressure: 1016 hPa
  • Visibility: 16KM
  • Wind Direction: SE
  • Wind speed: 7.4 km/h
  • Conditions: Haze

weather

Flight Conditions

Azam Saigol, Chairman PIA,  confirmed during a press conference that AP-BHO was Class-A checked just one month ago, indicating that the aircraft was in perfect condition.

While there was one instance of engine failure of the same aircraft back in 2014, it was replaced with a new engine and since then AP-BHO had operated smoothly without any issues being reported.

For flight PK661, there were 47 passengers on-board the ATR 42-500, indicating that the plane was pretty much with-in its load capacity.

Chairman PIA confirmed that flight PK661 was piloted by Salehyar Janjua, with flying experience of more than 12,000 hours.

Pilot of ill-fated PK661 had extensive experience of flying in northern areas, which means that he was well versed with the route and conditions where PK661 crashed.

Engine Failure And Ultimately the Crash!

Air Control Tower confirmed that flight PK661 signaled an engine failure at 4:12PM. Till the time the flight PK661 was flying smoothly at 13,375 feet.

However, as soon as the engine failure was reported, aircraft started descending — gradually at first.

Let’s have a look at flight data of PK661:

czflqyuwgaaonxs

Via (FlightRadar24)

The initial descent was gradual and seemingly controlled, until the aircraft reached 12,800 feet. This is when aircraft gained altitude of 50 feet and reached 12,850.

However, it started descending again — in a non-symmetrical manner — and reached 12,175 feet.

Flight PK661 must had become imbalanced by then as it lost irregular altitude during next few moments.

  • Flight started to bump starting 4:12PM — this is when it approached ATC and reported engine failure
  • PK661 kept loosing altitude and lost 2,000 feet (gradually) with-in next 60 seconds
  • Then a free fall and another 1,800 feet were lost with-in matter of seconds
  • PK661 Slightly stabled for few seconds and then lost another 2,000 with-in seconds
  • PK661 fell freely for over 4,000 feet to reach 8,250 feet with-in moments
  • PK661 gained some control and glided for few seconds before another free fall at around 4:13PM before disappearing from the radar

Here is what we are sure about:

  • One engine had failed
  • PK661 fell freely
  • PK661 was damaged structurally

Since PK661 fell freely, we can say with certainty that aircraft was not in-tact and it had lost its shape and failed to glide.

It must be noted here that ATRs can glide even if both engines are switched off / malfunctioned. Since PK661 was flying at around 13,000 feet — had it been in-tact — it could glide some 15-25KMs before hitting the ground.

However, an aircraft will fall freely if there’s any structural damage as hampered aerodynamics will not allow the aircraft to glide with a gradual descent.

Since we know that at least one engine had failed, there’s a chance that it splashed and damaged the wing attached to it, affecting the aerodynamics of the aircraft which ultimately brought it down with-in seconds to and resulted in a crash.

It must be noted here that pilots have a way of shutting down the engine. But before that you need to descend and reduce speed to match the aerodynamics of the situation the aircraft is in, which the pilots did — and is seen in the graph above.

You simply do no shut the problematic engine immediately. Instead, you bring the aircraft to a certain altitude and speed to make sure that the remaining engine is able to handle the load and aerodynamics.

And while the pilot was trying to do so, the failed engine probably caught fire or more likely exploded and damaged the wings.

It must be noted that there are steps involved in stopping a mid flight ATR engine and it includes performing certain checks, such as shutting down the fuel supply, shutting down the engine itself and so on.

Here is what seemingly happened:

  • Engine failed
  • Pilot reduced speed, dropped altitude — clear from above graph
  • Free Fall Due to Structural Damage
    • Pilot shut down the engine and
      • Shut down the malfunctioned engine, however, it was too late and it had exploded before that and damaged the wing
      • Stopped the working engine, and throttled the malfunctioned engine that triggered the explosion and damaged the wing

Here’s what seemingly didn’t happen:

  • Aircraft was a good height/speed, and chances of stall are unlikely
  • Aircraft didn’t run out of fuel, clear from the burns at the crash site

So the information we have so far indicates that the engine exploded and damaged a wing, impacting the aerodynamics and forced the aircraft to fall freely to ground with-in seconds of the incident.

It must be noted that complete details about the PK661 crash, with an authoritative conclusion is only possible after decoding more info from FDR, Cockpit Voice Recorders and other flight data recorders.

A conclusive investigation is must here, and reasons must be determined that brought down the PK661. This is not important for PIA only but for ATR as well, to avoid any future accidents.

It must be mentioned here that there are over 1,500 ATRs in service today — with almost similar specs — and a only a conclusive investigation will ensure safe travel on ATRs in the future.

Also Read: Crashed PIA Plane Had Engine Failures in Past #PK661

Tech reporter with over 10 years of experience, founder of ProPakistani.PK


  • Bohat afsoos hai khas kar Junaid Jamshed ka un ke gane main bauhat shauk sai sunta tha.Khas kar vital sings.

          • please note that Qadyanies also use net and their names like Muslims so umair, salman may be Qadyanies so avoid conflict with them

            • What if they aren’t Qadiyanies? How can you be so sure? Or you’re just assuming that they apparently would be just to make yourself and others happy that muslims are so amazingly good? Wake up. I heard this in my neighbourhood, from a muslim friend that he was listening to his songs and crying over his death and wanting me to listen to them as well. He certainly wasn’t a qadiyani, as I’ve know him and his family personally.

            • “please note that Qadyanies also use net and their names like Muslims so khalid may be Qadyani so avoid conflict with him”

              better?

  • AA, I JUST WANT TO KNOW THAT THERE ANY NO WAY (PARASHOOT ETC.) TO SAVE THE PILOT, OR PASSENGERS IN THIS CONDITION?

    • Parachutes require a lot of training. When someone is falling freely, they attain terminal velocity of around 195km/sec. Keeping posture and deploying chute correctly is nearly impossible without training. I know I would lose senses even if I am trained. Afterwards, landing is potentially killer unless the person is trained about that phase as well.
      The best course of action is to follow emergency survival guidelines and sticking to seats instead of panicking. Even then, chances of survival are very low. Look for videos and info about “freefall” and how did a few untrained people survive it. Its been more than 4 decades that survivors are mostly kids or flight staff, if any. Unfortunately, pilots are perhaps mandatory casualty in emergency. Their bravery must be saluted while they obviously attempt to keep the plane afloat, or try to steer it away from populated areas or avoid serious damage on impact if nothing else is working. They do it when they know their death is certain eventually. I guess no pilot lived to tell the tale. So we dont know what do they go through.
      From the blog post, it is obvious that the remarkable and evidently experienced pilot did his best to keep the plane safer but well fate had it. Inna Lillah wa inna ilaih rajioon. Its even sad to find out (if true) that pilot (saleh janjua) of this flight was son of another pilot (iftikhar janjua) whose plane crashed into a hilltop while the plane was about to land in Khatmandu in 1992. As usual, Nepalese turd authorities blamed pilots.

      If debris is scattered in a vast area, it is obvious that the plane unfortunately disintegrated midair (due to turbulence? sabotage?).

  • There should be completed video recording during its flight to check for all weather and engine and fight conditions to better monitor what is happening when a plane is going to crash. This will let know the exact reasons why engines / planes crash, and will guide in future designs of planes/engines.

  • Good analysis in this blog post. Well done. Well this is life, as much as we human beings try to control our life, we should realise that unfortunately we can’t control every thing. Unfortunate for the passengers and crew of this plane.

  • Good write Mr. Aamir Aattaa, the analysis covers all the aspects examined carefully. The graph looks ferocious and illustrates the later pattern clearly what happened to the flight. It is requested to expand this article with future outcome of the investigation.

      • Yes, if you understand the x-axis and y-axis the pattern not only is ferocious but also shocking, dreadful, distressing as well as frightening.
        Regarding google translate, its for assisting people like you.. :P

  • It all happened in just 3 Minutes (11:12 to 11:15), the plane probably was in total fire as soon as the flight radar stopped working.

  • Where did this analysis come from? So sad to get obvious details wrong.

    For example.

    * Then a free fall and another 1,800 feet were lost with-in a millisecond

    There are 1,000 milliseconds in a second. So that is 1,800,000 feet per second. Does that make sense to you?

    To put it in perspective, there are 3,280 feet in one km. Does anyone believe the plane dropped over half a kilometer in one millisecond? I honestly do not see understand how someone can look at flightradar chart and come to that conclusion.

    PEople, please, do not turn your branes off.

    • Free fall and glided fall are different, and graph pretty much tells what kind of fall was it.

      Please don’t argue, call this analysis wrong, but don’t argue :D

      • > Free fall and glided fall are different,

        Your brane is violently switched off. Meteors, which are big solid pieces of rock and metal like iron or nickel, burn up in the upper atmosphere (where air is NOT DENSE) at the speed of 50-70 km/second. Your post says the plane fell half a km in 1 millisecond, which is the same as traveling 500 km/second in DENSE atmosphere.

        Further more, Graph x axis is in milliseconds but significant changes are in seconds field. Maybe you should go argue with your optometrist.

          • 1 km in 1 second = 3,600 km in 1 hour
            That is Mach 3. You seriously believe that a plane (with unfunctioning engines) can suddenly drop THREE TIMES THE SPEED OF SOUND in one second? Do you understand anything about gravity or acceleration?

            You are either a failure at physics or trolling in your own posts.

            There is no way your post about 1,800 feet in 1 millisecond is correct, it makes no sense.
            There is no way your “correction” of 1 km in 1 second is correct, it also makes no sense.

            More you post, less you are trusted.

              • I am saying your post contains misinformation, and you are apparently too ignorant of math to figure it out even after I have pointed at specific calculations. Or maybe the fact is you don’t care you are publishing obvious falsehoods?

                • @shahidsaleem:disqus We all know @aamir7:disqus is not an Aviation Expert. He is a successful Pakistani Blogger with expertise in the same field. Being a blogger, he published this detailed analysis based article earlier than many other bloggers which is a great deal for him. We’re living in the society where even Giant Media Channels can’t provide us fair/factual news. All of the channels were claiming a female passenger as JJ’s wife just because of her lastname, Junaid. Also a fake audio clip played by some channels is another example. In a nutshell, we can’t expect total expert level and factual analysis by him or people like him. If he has written something wrong or did bad analysis, its your duty to share your knowledge in the form of comments as you did. But there’s no need of getting angry, blaming each other or using harsh words I think. I went through all the comments but your initial comments got my special attention, your point in this regard makes much more sense.

                  @aamir7 I appreciate the job you did in this article, its really fantastic but i think Shahid’s point is right. You can edit the article after paying some more attention to that if required.

                  Hopefully you guys wouldn’t mind my comment.

                  • Yes, he’s right. And I have edited the article based on his feedback. But he won’t stopp ther since he’s old troll, who just picks one thing and beats it forever.

                    My whole point of mentioning several hundred feet fall in milliseconds was to emphasize on free fall — to basically establish that structure was damaged — and I never claimed that falling speed (mentioned earlier) was the actual speed — as its not known yet, but he’s made an issue out of an analogy.

                  • Please go back and read my first comment. I did share my knowledge. I am not an aviation expert either (nor am I PhD in Physics) but 1,800 feet in 1 millisecond is OBVIOUSLY WRONG to me and I pointed out why.

                    And then even after I showed my maths the writer first commented about “1 km in 1 second” (also wrong) and then took over a day to correct the post.

                    And now in the comment here the writer says I am “trolling” and obviously saying BS by writing “I never claimed that falling speed was the actual speed” and it was “an analogy”.

                    Why do I call it BS? Because the post says “we will try to analyze available information and try to come up with possible reasons for the crash of flight PK661.” IN NO PLACE is it mentioned that 1,800 feet figure is a figment of the writer’s imagination. We are led to believe by that sentence that all the speeds, all the times, etc. are “available information” which means published by other entities.

                    Look, I do not make ANY MONEY when I post here. Yet when the writer posts absolutely obvious crap, he makes money, especially when it sensationalises a tragic accident that is on everyone’s minds and in the news.

                  • @aamir7:disqus I really appreciate that you edited the post based on Shahid’s feedback. This is what you should do being a good blogger and sincere to your field and you did it, great!

                    @shahidsaleem:disqus I do agree with your arguments. Yeah we know all of we cementers aren’t getting any money here but sharing our knowledge and opinion is our right. You utilized it in the right way by identifying wrong calculations, he tried arguing but later admitted your point and edited his article accordingly. What else is required now? nothing, so full stop. ;)

                    I think Shahid deserves appreciation for sharing right calculations and Aamir also for openly admitting and editing the article. so good job guys

                    (Feeling like a Baba G)

  • Hey guys, very nice article.
    Could you also post the speed va time graph for the flight.. similar to the altitude graph? I’m curious to see what that might look like, it might also indicate whether the plane went into a dive because of lack of speed (no lift) or physical damage like you say?

    • We don’t have its speed data as of yet. However, considering that descent was normal — in the start — we assumed that speed was sufficient and that it didn’t stall due to air-speed.

  • the reason behind the crash is corrupt government and PIA looters with old untested and ill maintained airplanes. stop giving us your false feedbacks, the plane had only one F*****in Engine and the president PIA hoped that it would reach destination, he and his family should be hanged till their necks break.

    • Sure, he is a Tech journalist and not Aviation Journalist… What do u think, Aviation is a discipline/faculty of “Technology” or something like “Human Sciences” or “Mind Sciences”??? Please use your brain before writing a comment….

      • Are you trying to say that Every “Tech Journalist” is an expert of Aviation/Related disciplines?

        In my “limited knowledge”, Aviation Journalists exist; who don’t make analysis on “why Note 7 explodes”.

    • I don’t know what qualifications he has to be called a “tech journalist”

      More like “tech enthusiast with a blog”

  • In a civilized world: Lets not discuss the reasons as competent authority is looking into the case. Wait for their feedback and not corrupt the mind of ordinary people with information they cannot understand.
    In Pakistan: Lets discuss the reasons as per our own mind and then create havoc if the investigation does not go our way… yeehaa!!!

  • Hmmmm So reasons cold be
    1.weak wings structure .
    2. Negligence in engine maintenance causing engine to explode and damage wing

    • @Jazz,
      I really like your fault tree analysis approach which is a qualitative technique to analyze a failure….Lets expand the weak wings structure event further to reach a basic event. Is it true for an aircraft 10 years old with reasonanble factor of safety!

  • PLEASE DO NOT TAKE THIS ARTICLE AS FINAL WORD.

    This article is crappy at best.

    ATR can fly with one engine. It is possible that pilot turned off the wrong engine. It is a very common aviation mistake and has happened in past leading to fatalities.

    If you ask any aviator to read this article he will tell you it was written by a 12 year old wannabe.

    I am sorry but this is factually incorrect.

  • This analysis was done by looking at 2 graphs, while sitting on a revolving chair and eating Cheetos.

  • Aamir bhai if you have any decency, you would not have published this analysis by a 12 year old. At least take an aviator’s take on this.

    Any experienced aviator will tell you that the most common aviation mistake is switching off the working engine. It is very likely that this has happened here which led to sudden drop in altitude and then crash.

    Very disappointing Aamir bhai.

    And please stop deleting comments ;)

    • Switching off the wrong engine wouldn’t had allowed the ATR to fall at this pace. You need to consider this. Falling freely will only mean that ATR’s structure was damaged, even one rudder gone could make it fall like it did.

      And which of your comment got deleted? This site is known for not deleting comments (except those with bad language)

      • Congratulations Aamir Brother on being expert in Aviation! May you succeed in become experts in everything else as well!

          • Ok I admin you probably know more then those retired generals! You probably deserve a medal for saving them time so they could get to there golf game today!

            Keep it up bro! I’ll warn Zubaida appa about upcoming competition!

          • CAA did no such thing. If it did, prove it by showing press release on their web site. In fact, if they did write that “milliseconds” then they are INCOMPETENT.

            Even ICBM launched from US to impact Russia travel no faster than 10 km/second when about to hit the target. Your numbers puts the plane falling faster than that without any rocket engines.

            It is a DAWN article and as clearly you can see in the comments other people have also commented on this.

            On one hand you make fun of people who believe in Water Car, on other hand you post thousands of feet per millisecond without second thought.

          • It was not picked by CAA and apparently the Dawn Editor does not know what a millisecond is.

            If anything, the article will be pulled soon but you are cementing your name as a guy who is misleading people.

            Enjoy while you can Aamir bhai or correct your behavior.

  • The ordeal last 3 minutes….RIP.

    Did anyone notice the systematic bumps starting at 11:10:35 (and the following bumps in the chart are of the same nature). Wonder if the engine started having issues then, which then escalated bringing it to its end.

  • How does an engine explode mid-air? It seizes, it heats up, it shuts down and propellers feather. Never heard of engine exploding.
    If it had a ripped wing the airplane would go into a spin or into something of uncontrollable oscillation.
    I would like see what the FDR brings up. I hope someone will investigate this and corrective measures are put into place.


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