Terminal Velocity

Discussion in 'The War In The Air' started by archivist, Oct 1, 2018.

  1. archivist

    archivist Well-Known Member

    Can anyone please help me out with a technical problem. If an airman jumped out of a plane without his parachute, I know that his terminal velocity would be around 120-125 mph but can anyone please tell me how far he would have fallen before he reached terminal velocity. The purpose of this is to help me assess the minimum height he could have fallen.
     
  2. canuck

    canuck Token Colonial Patron

    At lower altitude, approx. 10-12 seconds, falling some 450 m (1,500 ft) in that time. Around 15 secs from higher altitudes with variances based on atmospheric pressure, head down position, limbs pulled in, etc.
     
    HA96 likes this.
  3. Blutto

    Blutto Plane Mad

  4. HA96

    HA96 Member

    Wow, I am really impressed.
    I researched a jump of the US airman Conny Vogel. His para. did not or could not be opened. Sadly, he was killed with his legs up to the knees in the soggy groud of a potatoe field
    RIP


    Stefan.
     
    Last edited: Oct 8, 2018
  5. archivist

    archivist Well-Known Member

    Thank you Canuck,
    That is exactly what I wanted - a simple explanation that I can understand! (I am not a technical person) The necessary drop fits in well with the sort of height level that my target plane would be flying and even gives me a generous margin for error.
     
  6. Dave55

    Dave55 Very Senior Member Patron

    If you dropped something from a height, it would take 5.71 seconds to reach 125 MPH, not accounting for flapping arms. tucking, etc

    125 MPH = 183ft/sec

    32ft/Xsec^2 = 183ft/sec

    Xsec^2 = 5.71ft/sec

    X = 5.71 seconds

    Something falling for 5.71 seconds will travel for 522 feet before it reaches 125 MPH

    D= (32 x 5.71 ^2) / 5


    D = 1043/5

    D = 522 feet

    Lab conditions and not an airman, of course :)
     
    Tricky Dicky likes this.
  7. archivist

    archivist Well-Known Member

    Thanks Dave,
    That is another easy to understand formula! The conditions were that it was early hours of the morning (around 2 am) cold, wet and foggy with no significant wind. The airman had chest wounds/injuries and fell feet first but death occurred after impact - probably drowning in the deep bog. Major arm, leg and pelvis injuries were probably caused by the feet first impact and the body was found 6-9 feet down in the bog.
    It was found almost exactly one mile from the end of the runway and with the distances he fell (according to your figures) that looks like the pilot was trying to land i.e. he was in a low approach. All of this makes sense but unfortunately the plane and the rest of the crew were never found. So it looks like they are still in that bog - which is known to be well over 30feet deep in places.
     
  8. Harry Ree

    Harry Ree Very Senior Member

    In wartime reports,It was always said that the terminal velocity was 120 mph and looking at the graph indication of 50 metres/sec,it equates to 112 mph which reflects that understanding.

    There is the case of Nicholas Alkemade a Gunner of No 115 Squadron,out of Witchford on a raid to Berlin on 24 March 1944 who bailed out without a parachute and survived.Unable to locate his parachute he decided to leave his stricken aircraft without a parachute and survived after falling into deep snow.His velocity may have been reduced by falling through trees.The Germans refused to believe he could survive a jump from 18000 feet without a parachute.....thought initially he was spy,he was finally accepted as a POW.

    There was the specification of the parachute harness and clip tensile strength which would only take one parachutist.In an emergency,a crewman without a parachute would likely clip on his harness to another crew member's harness and conduct a tandem jump.Unfortunately when the parachute opened ,it applied a shock loading to the clip harness which failed, resulting in the second man falling to his death.I cannot see it recorded where a tandem jump in these emergency circumstances was successful during the war.

    If the parachute does not deploy,there is the danger of a "roman candle" being the outcome and a fall to death usually occurs.Parachute rigging being fouled up can also increase the terminal velocity and lead to injury and worse.Anne Marie Walters related that when she jumped on to her DZ at Gaberret in the Gers,her rigging was fouled and her rapid descent gave her reason for concern but through her training she was able to recover by kicking and kicking until the rigging became untangled and the parachute fully opened.

    As I recollect from limited parachute training....not actually jumping.A fundamental requirement of ensuring that the leg posture,ie,feet and knees together for safety on landing and a roll on to leg,thigh and backside.A normal parachute landing was said to be similar to jumping off a 12 foot wall but in our training the jump was off a 6 foot wall.

    Ground wind speed is crucial to prevent injuries and it thought that a wind speed of more than 15 knots increases the possibility of injuries being sustained on landing.
     
    Tricky Dicky likes this.
  9. canuck

    canuck Token Colonial Patron

    My brother took his first parachute jump in higher than average winds and has 3 pins in his right ankle to show for it. They scrubbed the remainder of the jumps that day after watching his descent.
     
  10. Dave55

    Dave55 Very Senior Member Patron

    Horrible way to die. Poor man.
     

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