A United Airlines 737 presented onlookers with an unusual sight when it tipped up and sat on its tail, during disembarkation, last Friday.
The incident involved United Airlines flight UA2509. United apparently uses this particular flight number for chartered flights, which is what this was. Friday’s flight originated in Los Angeles (KLAX), heading to Lewiston Nez Perce County Airport (KLWS), in Idaho, USA. This airport typically sees service from regional airlines, flying the likes of CRJ200s or something smaller.
So, who charters an entire United 737, and a 737-900ER at that? In this case, it’s the USC (University of Southern California) Trojans, an American football team. The incident happened ahead of their Saturday game against Washington State University’s Cougars.
The United crew flew their 737 into Lewiston without incident. They parked normally on a stand, and disembarkation began. According to local reports, all football players left the aircraft without issues. Remaining on the aircraft was the team’s coach, football team staff and members of the United crew.
According to some sources, United expected ground crews to attach a tail support stand on their 737. We don’t know if these would be airline crew members or airport staff, since 737s don’t visit this airport regularly. Pictures show that ground crews had removed a lot of luggage from the front luggage area of the aircraft.
Tail Support Stands And Unloading
There were no injuries from the incident. The crew ‘righted’ the aircraft and everyone disembarked safely. And perhaps just as important for the USC team, they won on Saturday. So this unusual experience of their coach’s apparently didn’t affect them! But why did it happen? And what is this “tail support stand” that this United 737 needed?
Some crews affectionately call it “the pogo stick”. When aircraft are ready to fly, they don’t need it. An airliner’s centre of gravity (CG) is always a bit forward of the wing. So if the main gear is under the wing, as in this case, the plane should sit comfortably on all of its wheels. However, during loading and unloading, things can vary quite a bit. This was the case with this United 737.
In the case of most aircraft, crews can avoid such situations with a bit of care and attention. You’ve probably had to wait when leaving the plane because someone is taking too long gathering their overhead luggage (and jacket, and duty-free bags, and…). If a few too many people near the back of the plane are stuck this way, crews will stop people near the front from leaving.
In the United 737 in Lewiston, the luggage may have also played a role. In any case, such incidents do happen from time to time. Longer aircraft need a bit more attention or a tail support stand. And the 737-900ER is rather long. Some aircraft actually incorporate a retractable “pogo stick”. Older planes with rear airstairs like the 727 didn’t need it, because the airstairs themselves effectively played this role.
The United 737 And… What About That Tail Skid?
Tail strikes like this are damaging, but not nearly as much as one during landing or takeoff. This United 737 has already flown again after this incident, to Houston (KIAH). This was most likely a positioning flight. But the plane cruised at FL390, indicating that there were no concerns regarding its pressurisation. The aircraft is a 737-924ER(WL), with registration N78448. It is just over nine and a half years old.
Finally, a small footnote. You may know that most 737 airliners these days have a tail skid, and this United 737-900ER is one of them. But if you look at the ‘tip-up’ photo a bit more closely, it looks as if the tail skid is in the wrong place! So, what is that all about? Why have a tail skid if it’s not going to be the first thing that hits the ground?
The answer is that the skid isn’t there for static incidents, like this one here. For most 737s, it works on takeoff only. Even below normal rotation speed, the wings will support enough of the plane’s weight, for the main gear suspension to extend. And this means that the tail skid WILL be the first thing to hit the ground, in this scenario.
For landings, longer (i.e. more prone to tailstrike) 737 models, including this United -900ER, have a Short-Field Performance (SFP) kit. This kit hydraulically extends the tail skid another 5 inches (12.7cm) during landing, to protect the tail. But after the landing, the skid retracts again. So it would not protect the tail when the aircraft is simply parked!
Hopefully, United will manage to return this aircraft to revenue service soon.