How I killed two party members by inventing the dirigible.

So I'm like playing Lelk, same character I posted about last time, and basically he is this prince person defending a town from this usurper guy and his army, all I got to prepare my defense with is a bunch of wizards, no warrior type people at all. Sicne I'm playing the prince I have to come up with the defenses- most of these were reasonable things like catapults and dropping rocks from the wall and digging ditches and putting sharpened pieces of wood in them.
But to my way of thinkig, it just wasn't enough so I'm like still thinking of ways to defend the town, while the others are like training the militia.
So suddenly I have this idea and ask:
Me: "Hey do we have any canvas?"
DM: "Yes we have some..."
"Cool can we make some....watchmacallit....trapeze....flying things..."
other Player: "Hang Glider?'
Me: "Yea a hang glider so that I can get on it and fly down to the enemy commander and attack him?"
Player 2: "No wait, how about making a dirigible from the canvas?"
me: "Yea dirigible! Lets make a dirigible so that we can bomb the enemy!"
DM: "roll for the wizards to accept the idea and a second role to build it."
Me, I roll and....two 20's
Now see my DM just decides to roll a d100 whenever he is not sure of the outcome and guess what. He rolled the d100 twice and....95 and 97.
My DM is facepalming my now and going "oh god."
The result was, was that wizards I commanded thought it was like the best idea ever then built a dirigible without any problems whatsoever, on a 1 in 4 million chance.
Then I proceeded to get in my party of course follows, we fly over the enemy camp and they are like "What is THAT!?" since they never saw a dirigible before and think its some kind of UFO.
Then of course I start bombing. Problem was that only two bombs were made, so I like threw out the two bombs then accidentally threw the third "Bomb"- the party's fighter, who took a lot of damage and died
Of course the dirigible bombing causes the enemy to attack the town immediately, I fly back to the town and command the people to defend, and on my roll I get another 20, thus perfectly defending the town.

But next session the party's wizard who had gone to the other side being a spy who had been absent the session I invented the dirigible, had been revealed to be have been killed in one of the bombs I dropped on the enemy camp because of a bad 1d100 roll. Thats how I killed two party members by inventing the dirigible, in a medieval town with a team of npc wizards.