With the denied takeoff test, the ARFF can approach the aircraft but fail to apply any material over a period of time to account for real-world response times. The ARFF are usually at the airport site, especially for any place that receives a 747, but they do not usually sit on the side of the runway unless an emergency is declared prior to arrival. How they set for pilots not to overstep the plane's limits. Second, it sets maintenance requirements so airlines know which parts will last and how long. The USAF lost the AC-130J brand new because the plane flipped over for a few seconds during testing. It regained its safety and landed, but had to be canceled because it exceeded safety thresholds, according to the maintenance manual. That's why this test is important. Yes, experienced and impartial engineers apply their knowledge and experience, unfortunately, those efforts go to waste when sub-industry and analogous parts are installed. Percas that have not been tested should not be fitted.