Editing Tiltrotor (section)

===Speed and payload issues===
The tiltrotor's advantage is significantly greater speed than a helicopter. In a helicopter the maximum forward speed is defined by the turn speed of the [[helicopter rotor|rotor]]; at some point the helicopter will be moving forward at the same speed as the spinning of the backwards-moving side of the rotor, so that side of the rotor sees zero or negative [[airspeed]], and begins to [[stall (flight)|stall]]. This limits modern helicopters to cruise speeds of about 150 [[knot (unit)|knot]]s / 277&nbsp;km/h. However, with the tiltrotor this problem is avoided, because the proprotors are perpendicular to the motion in the high-speed portions of the flight regime (and thus not subject to this reverse flow condition), so the tiltrotor has relatively high maximum speed—over 300&nbsp;knots / 560&nbsp;km/h has been demonstrated in the two types of tiltrotors flown so far, and cruise speeds of 250&nbsp;knots / 460&nbsp;km/h  are achieved.<ref name="Norton V-22"/>

This speed is achieved somewhat at the expense of [[Payload (air and space craft)|payload]]. As a result of this reduced payload, some{{Who|date=October 2014}} estimate that a tiltrotor does not exceed the transport efficiency (speed times payload) of a helicopter,<ref>{{cite book|url=http://www.nap.edu/books/0309064295/html/82.html#p0200064b99960082001|title=Front Matter - Naval Expeditionary Logistics: Enabling Operational Maneuver from the Sea - The National Academies Press|website=nap.edu|year=1999 |access-date=1 April 2018|doi=10.17226/6410|hdl=10945/62493 |isbn=978-0-309-06429-3 }}</ref> while others conclude the opposite.<ref name=cs2tech/> Additionally, the tiltrotor propulsion system is more complex than a conventional helicopter due to the large, articulated nacelles and the added wing; however, the improved cruise efficiency and speed improvement over helicopters is significant in certain uses.  Speed and, more importantly, the benefit to overall response time is the principal virtue sought by the military forces that are using the tiltrotor. Tiltrotors are inherently less noisy in forward flight (airplane mode) than helicopters.{{citation needed|date=May 2009}} This, combined with their increased speed, is expected to improve their utility in populated areas for commercial uses and reduce the threat of detection for military uses. Tiltrotors, however, are typically as loud as equally sized helicopters in hovering flight. Noise simulations for a 90-passenger tiltrotor indicate lower cruise noise inside the cabin than a [[Bombardier Dash 8]] airplane, although low-frequency vibrations may be higher.<ref>Grosveld, Ferdinand W. et al. "[https://ntrs.nasa.gov/search.jsp?R=20130013992 Interior Noise Predictions in the Preliminary Design of the Large Civil Tiltrotor (LCTR2)]" 20130013992 ''[[NASA]]'', 21 May 2013. Accessed: 9 June 2014.</ref>

Tiltrotors also provide substantially greater cruise altitude capability than helicopters. Tiltrotors can easily reach 6,000&nbsp;m / 20,000&nbsp;ft or more whereas helicopters typically do not exceed 3,000&nbsp;m / 10,000&nbsp;ft altitude.  This feature will mean that some uses that have been commonly considered only for fixed-wing aircraft can now be supported with tiltrotors without need of a runway. A drawback however is that a tiltrotor suffers considerably reduced payload when taking off from high altitude.