MU-2B 60 Marquise
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 72; Flight Crew Total 1000; Flight Crew Type 398
Aircraft Equipment Problem Less Severe
Aircraft Aircraft Damaged; General Maintenance Action
Aircraft
We flew our MU-2 Marquise (MU-2B-60) to Scottsdale; AZ (SDL) with a fuel stop in ZZZ.  While in flight in VMC conditions at FL220 on an IFR flight plan northwest of Albuquerque; I heard a loud bang from the right side of the plane behind the cockpit.  All cockpit indications were normal; all flight instruments were normal; and there was no shudder or movement of the aircraft.  A passenger in the back called out that a window was broken.  Upon inspection we determined that the outer pane (there are three panes per window) of the forward most passenger window on the right side of the plane had failed; with the central part of the window missing and shards around the frame.  Shortly thereafter; the master caution light came on as well as a cabin altitude light on the annunciator panel.  The pressurization system indicated the cabin altitude had climbed from approximately 5;000 feet (pre incident) to just over 10;000 feet and cabin differential pressure had dropped from approximately 5.5 paid to 2.5 paid.  The right engine sounded fine; no unusual vibrations (including the right spinner); and everything else appeared normal.  As we were literally over the middle of nothing; I notified ATC of the situation but told them I was not declaring an emergency but wanted to descend to a lower altitude. The aircraft checklist treats loss of cabin pressure as an emergency and calls for decreasing altitude to a one not requiring oxygen.  With center approval; we made a slow descent (approximately 500fpm) down to FL180 which dropped the cabin differential pressure and cabin altitude to under 10;000 feet.  I also looked at divert options should things get worse.  As there were no airports with which I was familiar; all flight controls were fine and indications were normal; I elected to proceed on to Scottsdale but was prepared to divert to another field should conditions change.  I also requested a slower than normal descent into Scottsdale (we normally descend at 1;500-2;000fpm; in this case we started descent early and descended at 500fpm.  Ultimately we made it to Scottsdale (SDL) with no other issues.  Upon inspection after landing; additional damage beyond the window was evident.  Specifically; I noted the following damage:- The right propeller had impact marks consistent with the propeller having struck the window plexiglass.  Specifically; paint was scraped in various areas on the front and back of the propeller blades about 4-8 inches from the tip; one blade had a slight 'dent' in the leading edge and a scrape mark on the back of the blade and the blade ahead of it (in direction of rotation) had a 'notch' in the leading edge with the metal bent inwards and forwards consistent with an impact as well as significant paint scraped off on the front and back sides of the blade.- There are multiple small chips in the paint and small dents in the right side of the fuselage and upper surface of the landing gear doors consistent with impact.- The leading edge of the right horizontal stabilizer has about a 4' cut in the de-ice boot and about 6' of the leading edge are bent in (as compared to the normal leading edge curve) consistent with and impact.  The aircraft had last been in maintenance for the 100 hour inspection in March of 2014.  At that time; per an FAA airworthiness directive; all windows were measured for thickness and found to be within standards.  The airplane functioned as designed and the inner panes prevented total loss of cabin pressure as well as all of the noise and slipstream associated with an opening to the exterior when in flight.  All flight controls and the engines functioned normally.  As Pilot in Command (with my family the passengers on board) my focus was on maintaining aircraft control; determining what had happened; following the checklist and then making an informed; deliberate decision on what further actions should be taken.  Given the inhospitable terrain below; the fact I was not familiar with the small; isolated airports along the route of flight; my familiarity with Scottsdale; the fact it had a tower and emergency services should they be required as well as maintenance facilities; I made the decision to continue on towards Scottsdale.  At all times I was prepared to immediately divert to an alternate field should circumstances change.  I was also prepared to shut down the right engine should it start behaving in an abnormal manner or demonstrate any sort of unusual vibration.  I discussed my circumstances with air traffic control and explicitly stated I was not declaring an emergency.  They were very helpful in pointing out various airports along my route of flight; runway lengths and directions and at each case I had an identified airport to turn towards should I need to divert.  I also used the Forflight software on my iPad to monitor the area and look at potential alternate landing sites.  It is my belief that ATC supported me as PIC in dealing with the incident and contributed to our ability to safely complete the flight without further damage or any injury.
MU-2B-60 pilot reported outer pane of a cabin window failed and contacted the right propeller and horizontal stabilizer when it departed the aircraft. Some pressurization loss was noticed so the pilot descended and continued to destination.