There have been many aviation accidents in history, some of which are both unfortunate and lucky. The accident we are talking about today is very interesting.
On 19 December 1946, a British Rail Air Transport DC-3 was preparing to take off from London Airport to Glasgow. The DC-3 was used by the U.S. Army as a military transport aircraft in World War II, and its military model was the famous C-47.
（DC-3）
It was a routine flight with a crew of 4 people and 1 passenger. On the day of takeoff, the weather was very cold, and it was snowing and windy, so the airport was decided to be closed, the inbound flights were no longer accepted for landing, and the outbound flights were delayed for a long time.
Before the plane was ready to take off, it had been waiting for more than 1 hour, and after receiving the take-off command, Captain Johnson immediately increased the throttle, increased the speed of the engine, and began to run and take off. When the speed of the plane reached 85 knots, he began to pull the rod, and the plane left the ground and began to climb. But as soon as it took off, the captain realized that the situation was not good. Because this aircraft for unknown reasons, that is, there is no power to climb, there is always no way to reach its climb curve.
（DC-3）
At that time, it was already difficult to give up takeoff or return home, and the captain had to bite the bullet and try to lift the plane, so he flew to the block.
On the take-off route, there were houses and buildings, and when flying to the block, a two-story house appeared in front of the plane. Under normal circumstances, when it came to this location, the house should be far below the plane, but because the plane could not climb, Johnson had no choice but to try to wipe the edge of the roof of the house and fly over. But unexpectedly, the plane directly hit the two-story house.
The house was a solid masonry structure, but the plane did not hit its solid wall, but hit the roof. The moment the plane hit the roof, the impact was still very large. The two wings snapped instantly, and bent rearward, and the entire fuselage section went directly through the roof. Since the impact consumed most of the kinetic energy of the aircraft, the aircraft was just set on the roof. But thankfully, everyone was unharmed.
What's more interesting is that in this hit house, there is a 4-month-old baby who is still sleeping, with a loud bang, and a lot of debris on the roof fell without unfortunately touching the baby, and the baby didn't even wake up, and it was unscathed.
After investigation, it was found that the reason was actually very simple, that is, there was ice and snow accumulation on the wing.
The plane had already been de-iced and snow removal before takeoff, but because it took more than one hour to wait for takeoff release and it was snowing, the snow began to accumulate on the wings again. Pilots had thought that the air currents might blow the snow and ice off after takeoff, but the humid British climate allowed the snow to quickly freeze on the wings.
In this way, the shape of the wings was destroyed, and they were no longer the most aerodynamic and efficient shapes that the designers sketched on the drawings of those years, but a very bulky and terrible appearance. Such a wing, at the stage of climbing, will lead to a serious separation of the air flow, which will simply not be able to generate sufficient lift. Therefore, how the captain pulls the rod, the plane is also weak to climb.
In fact, the plane was on the verge of stalling, but it hit the house and hit the relatively fragile roof part. If it falls directly to the ground, the consequences are unimaginable. Because it hit the roof, the impact of the roof absorbed the kinetic energy of the aircraft, and the height of the house ensured that the plane would not fall to the ground, so it was equivalent to completing an unconscious forced landing without risk.
Finally, the plane was hoisted by a crane, and this photograph remains in many archival institutions today, still a typical aviation safety incident. The cause of the accident was that the snow and ice of the aircraft were not removed, causing the plane to stall and fall. The captain's name was Johnson, and because he successfully completed this landing on the roof and no one was injured, his peers gave him the nickname "Roof Johnson". I don't know if the captain was happy or worried when he heard such a nickname.
After this accident, people have a deeper understanding of ice and snow removal. After all aircraft have completed de-icing in cold weather, there is a time limit for takeoff. If the take-off wait exceeds 45 minutes, or more, then the aircraft cannot take off immediately, and must carry out secondary de-icing and snow removal operations to meet the take-off requirements.
Every accident in history has put forward better experience and reference for our later safety guidelines.