First Deck Landing F-35B / USS Wasp

One place to look: MORE AT the JUMP!

Vertical Power By Eric Hehs Posted 15 September 2007

http://www.codeonemagazine.com/article.html?item_id=32

"Development Testing In Detail
"Most of our development testing in Florida is associated with low speeds and low altitudes, the lower left-hand corner of the flight envelope," notes Mark Tracy, manager of test operations for Pratt & Whitney at the Florida test site. "We are mitigating the risk for the powered lift flight test program for F-35B. Our work here verifies that the propulsion system will produce the amount of downward thrust needed for a successful flight test program for the F-35B and later for a successful real-world operation."

Recent developmental testing in Florida has focused on a redesigned inlet shape for the lift fan to get more lift and performance and to reduce flow distortion at the face of the lift fan. "The inlet is at ninety degrees to the airflow, so it presents a unique situation," explains Tom Sylvester, a senior engineer for Lockheed Martin present for these particular tests. "We used traditional methods for the initial design, but they just don't work well for a lift fan inlet because of the short distance between the inlet lip and the face of the fan. Unlike more traditional inlets, the airflow doesn't settle out before it gets to the fan surface."

The differences between the original inlet (called the development inlet) and the redesigned inlet (called the flight inlet) are imperceptible to an untrained eye. "The lip of the new inlet is only slightly different — an inch or two wider on the sides and a little taller," Sylvester explains. "The fan itself didn't change, but the inlet door was re-contoured to close securely against the new shape."

Northrop Grumman produced a metal/composite model of the new inlet shape. The model includes an aerodynamic fairing that replicates the fuselage area around the inlet that affects airflow into the inlet. The C14 test stand structure was modified for this model, which was installed on the stand with the rest of the vertical lift system in March 2007.

The vertical lift system with the new inlet and door combination was put through 116 hours of testing. During these tests, a crosswind generator used for testing effects of crosswinds on commercial jet engines was set up next to the test stand. The performance of the new inlet design was evaluated in crosswind angles of ninety degrees and wind speeds up to thirty-five knots.

The testing reduced a lot of un-certainties. "The lift fan performed better than we predicted," Sylvester explains. "The thrust numbers needed for hover are there." The biggest success is the additional thrust achieved from going to the development inlet to the flight inlet. "We increased the thrust and reduced the distortion in the lift fan, which will improve the durability and longevity of the system."

"The results were excellent," says Fran Ketter, research engineering director for Lockheed Martin and the program management interface for F-35 propulsion integration. "The inlet redesign resulted in significant improvements...."
__________

INGENIA ISSUE 41 DECEMBER 2009:

A FLEXIBLE JET FIGHTER

http://www.ingenia.org.uk/ingenia/issue ... /mehta.pdf (0.5mb)
___________

http://www.theengineer.co.uk/in-depth/r ... 08.article
_________

http://www.aviationweek.com/aw/blogs/de ... d&plckScri

H/T to SNAFU: F-35B struck down below....

http://3.bp.blogspot.com/-x91BlQ_TeOA/T ... 37-007.jpg

The landing and approach appear to be smoother than those done by Harriers, which I guess they should be in this era but still it's very impressive how rock steady it appears to be.

A Harrier landing for comparison:
http://www.youtube.com/watch?v=hYen_G-g ... r_embedded

Pilot's best friend: digital flight control systems.

'Vertical Validation’ by Guy Norris/Los Angeles
Aviation Week & Space Technology/October 3, 2011

“…Testing has also focused on the translational rate command (TRC) mode, which in the hover allows the pilot to make small positional corrections and which brings the aircraft to a standstill if the pilot releases the controls. “It is used to capture the current longitudinal groundspeed and is important for precise positioning in shipboard operations,” says Wilson.

On the Cooper-Harper rating scale used by test pilots to evaluate handling characteristics, pilots gave an average rating of 1.77 for descent and 2.28 for landing in baseline vertical-landing mode. For the TRC mode, pilots rated descent at 1.52 and landing at 2.04. The scale ranges from 1 to 9, with 1 representing excellent characteristics and a low workload task and 9 representing major deficiencies and intense pilot compensation required to maintain control….”

Youse will have to buy the magazine....

Anyone know where to get a better image of the F-35B tail logo (or what it is) please? Thanks.

Now
Take note that it did so without AB power.

http://youtu.be/Ake76DI5iNw?t=1m55s

I noticed in this clip just a touch of AB right after the wheels leave the ground...insurance power by the pilot?

Just curious.

Z

My thought would be that since there are many different test point being done, it could be one of them (cat did not produce expected push) or the F-35C was heavier in that shot.

.......................

That was a neat trick Ztex to have the video start there.

There was a thread about the 'automatic' afterburner enhancement during the catapult shot. The A/B is not at full power before launch but goes there if required during the launch. I'll go find the thread now. This is designed into the sequence not as an afterthough as is with the Super Hornet for example. Watch this space. And I mentioned Ztex in a good way.

Scroll down the page here to the variable A/B info:
How have your opinions of the JSF changed over the years?
http://www.f-16.net/index.php?name=PNph ... r&start=90

And here it is again anyways...

F-35C completes first jet blast deflector testing

http://www.navair.navy.mil/index.cfm?fu ... ry&id=4691

"...Each Nimitz-class aircraft carrier has a JBD for each of its four catapults. The size, cooling configuration and angle to the catapult vary slightly between the four, so the test team had to repeat various tests – military and limited afterburner power takeoffs – for the various JBD configurations...."
____________________

JBD Testing A Key Step For Joint Strike Fighter Aviation Week & Space Technology Jul 18, 2011 p. 84 by Amy Butler | Joint Base McGuire-Dix-Lakehurst, N.J.

http://www.navair.navy.mil/lakehurst/nl ... esting.pdf (125Kb)

"...Lockheed Martin test pilot Dan Canin commanded different levels of engine power for various intervals. One example of a cycle is 10 sec. of standard military power, 30 sec. of limited afterburner and another 60 sec. at idle...."
&
"...Even without the more extensive data provided by today’s sensor array, Super Hornet engineers gained valuable experience during JBD trials that led to a change in how the aircraft is launched. During testing, hot air was inadvertently recirculated into the air intake of the Super Hornet, prompting a “pop stall,” or hiccup in the airflow for the propulsion system. The result was a dangerous fireball coughing from the back of the Super Hornet, says Briggs.

The design fix was the creation of a limited afterburner setting for launch. Engineers crafted software such that the engine is at 122% of military power when a pilot sets it to afterburner. By the time the jet reaches the edge of the deck, the system automatically opens the throttle to full afterburner at 150% of power without intervention by the pilot, says Briggs.

Having completed the first phase of JBD trials with a single F-35C, engineers are eager to test a more realistic scenario with one aircraft in front of the deflector and one behind.

Because of this lesson, the limited afterburner setting was designed into the F-35 in its infancy...."

It's pretty simple really. Side doors offer no directional flow for the air, hence distortion since airflow is indirect. The new door is heavier and creates more drag, but the offset is better airflow (less distortion) and better performance.

How the flight control surfaces and nozzle perform shown in this 'slow motion' video at one eighth speed Ship Short Take Off (STO) USS Wasp 04 Oct 2011

'Vertical Validation’ by Guy Norris/Los Angeles
Aviation Week & Space Technology/October 3, 2011

“…Testing has also focused on the translational rate command (TRC) mode, which in the hover allows the pilot to make small positional corrections and which brings the aircraft to a standstill if the pilot releases the controls. “It is used to capture the current longitudinal groundspeed and is important for precise positioning in shipboard operations,” says Wilson.

On the Cooper-Harper rating scale used by test pilots to evaluate handling characteristics, pilots gave an average rating of 1.77 for descent and 2.28 for landing in baseline vertical-landing mode. For the TRC mode, pilots rated descent at 1.52 and landing at 2.04. The scale ranges from 1 to 9, with 1 representing excellent characteristics and a low workload task and 9 representing major deficiencies and intense pilot compensation required to maintain control….”

Youse will have to buy the magazine....

Any idea how the Harrier ranks?

Looking for that Harrier info - in the meantime...:

http://history.nasa.gov/SP-3300/ch4.htm#27

"...In concluding this section, it is appropriate to highlight what may be the most important contribution of the flying qualities evaluation programs and experiments conducted on the variable stability aircraft at Ames. This, of course, was George Cooper's standardized system for rating an aircraft's flying qualities. Cooper developed his rating system over several years as a result of the need to quantify the pilot's judgment of an aircraft's handling in a fashion that could be used in the stability and control design process. This came about because of his perception of the value that such a system would have, and because of the encouragement of his colleagues in this country and in England who were familiar with his initial attempts. Characteristically, Harry Goett spurred Cooper on in pursuit of this objective.

Cooper's approach forced a specific definition of the pilot's task and of its performance standards. Further, it accounted for the demands the aircraft placed on the pilot in accomplishing a given task to some specified degree of precision. The Cooper Pilot Opinion Rating Scale was initially published in 1957 (ref. 62). After several [27] years of experience gained in its application to many flight and simulator experiments and through its use by the military services and aircraft industry, it was subsequently modified in collaboration with Robert (Bob) Harper of the Cornell Aeronautical Laboratory and became the Cooper-Harper Handling Qualities Rating Scale (fig. 66) in 1969 (ref. 63). This rating scale has been one of the enduring contributions of flying qualities research at Ames over the past 40 years; the scale remains as the standard way of measuring flying qualities to this day. In recognition of his many contributions to aviation safety, Cooper received the Adm. Luis de Florez Flight Safety Award in 1966 and the Richard Hansford Burroughs, Jr., Test Pilot Award in 1971. After he retired, both he and Bob Harper were selected by the American Institute of Aeronautics and Astronautics to reprise the Cooper-Harper Rating Scale in the 1984 Wright Brothers Lectureship in Aeronautics...."

Figure 66. Cooper-Harper Handling Qualities Rating Scale.

http://history.nasa.gov/SP-3300/fig66.jpg

Just something interesting perhaps for those USAF inclined.

Flight Control Design – Best Practices

http://dodreports.com/pdf/ada387777.pdf (4.6Mb)

“2.1.4 Hawker-Siddeley AV-8 Harrier
Several problems showed up early in low-speed, low-altitude operation of this single engine VTOL fighter. This aircraft along with several other VTOL concepts shared a strong requirement for relatively large roll control power needed to trim in sideward/sideslip flight and yawing manoeuvres. The positive dihedral effect (rolling moment due to sideslip) introduced from a combination of aerodynamic-induced and engine induced flow was large enough to cause several accidents. For example, a fatal accident occurred in the late 1960s involving a first Harrier flight by a USAF pilot. In this case, a skidding right turn was made at 90 knots to avoid flying over a photographer shortly after takeoff. Because of excessive left slideslip, the aircraft rolled abruptly in spite of full opposite aileron input. The aircraft banked beyond 90 deg before the pilot ejected.

The lessons learned from this accident are straightforward. The pilot did not appreciate or understand the need to minimise sideslip in an airspeed regime where inherent directional stability was low, allowing directional/roll divergence to occur. Dealing with this particular departure requires mandatory use of rudder to reduce sideslip to recover from the roll-off. Instinctive use of aileron to reduce bank angle divergence will aggravate the situation because of adverse yaw generated by aileron deflection. {Comment: Can we assume we have passed by this kind of a problem? Will this problem of roll/yaw coupling return in a different form as we consider tailless configurations with marginal directional stability? Are there new lessons to be learned (or old ones re-learned) about roll/yaw coupling? Lastly, was this a training lesson?}”

From same 'sauce' above...

3.4 CONTROL LAWS DESIGN FOR VAAC HARRIER
‘Vectored thrust Aircraft Advanced flight Control’ (VAAC) is a UK project, which is managed by the Defence Evaluation and Research Agency. The project [Shanks, et al] is investigating the low speed flight control, handling and cockpit display concepts applicable to an aircraft to replace the Harrier. As part of the project, British Aerospace have designed a ‘two inceptor’ pitch control law which has been successfully demonstrated in a series of flight trials in the VAAC Harrier experimental research aircraft. With the two inceptor control strategy, the aircraft’s pitch stick, throttle lever and nozzle lever (for thrust vectoring) are replaced with right hand and left hand inceptors for controlling the aircraft in pitch. Such an arrangement involves a high degree of automatic control of the thrust vector.

Through involvement in this programme, the lessons learned with regard to pitch flight control laws are mainly associated with the handling of the aircraft during the transition between wing-borne and jet-borne flight (and vice-versa), and at low speed and in the hover:...

... | The early standard of the control law used an airspeed-triggered switch to transfer from pitch rate to height rate demand modes, with associated signal equalisation. This proved to be unnecessarily complicated and introduced a discrete, and undesirable, change in handling qualities. The control law was developed to include airspeed blending between the modes, leading to a significantly easier implementation and providing continuity of handling characteristics.

| Unlike a conventional aircraft, where full primary control surface deflections are rarely (if ever) used, the nozzle and throttle controls of a VSTOL aircraft are often operated on their limits, for example: to achieve maximum acceleration or deceleration performance, and when operating close to the hover with a low thrust margin. Since the thrust vector became part of a closed-loop system which involved integral control, appropriate integrator conditioning logic was required.

| Flight testing showed that the two-inceptor control strategy resulted in a large reduction in pilot workload, when compared with a three-inceptor arrangement, during the transition from wing-borne to jet-borne flight and hover. The demonstrated reduction in pilot workload was mainly due to the automatic axis transformations inherent in the control law, whereby the pilot’s thrust vector commands were in inertial axis rectangular coordinates (where appropriate) rather than body axis polar coordinates.

Subsequent to the development of the pitch laws, BAe have designed lateral/directional control laws for the VAAC Harrier [see Lodge and Runham], resulting in some further lessons learned:

| Care must be taken during pilot-in-the-loop simulation assessments. The lack of roll acceleration cues can result in a request for an increase in roll bandwidth, which when subsequently flown on the aircraft may result in an over-active response.

| Modelling fidelity is important for development testing; problems showed up in the flight test phase that previously had not been apparent, due to the lack of sensor noise modelling in the simulation model.

| The use of auto-coding for generation of the aircraft’s embedded flight control laws enabled rapid progress to be made, once flight testing had commenced. Once deficiencies had been identified in the control laws, changes could be identified, tested, implemented, and flown on the aircraft, on the same day.

| Once the pilots had become familiar with the response produced by translational rate control (TRC), it was found that they wanted more authority than was initially provided. Currently a full authority TRC input will produce a ground-referenced lateral velocity of 20 knots.

| Although two-axis (pitch and bank) TRC in the hover has shown that a significant decrease in workload is achievable, questions have been raised as how best to implement the TRC pilot interface. Of the various control options tried (centre stick, left and right hand mini-stick tops), the left-hand mini-stick top mounted on the throttle has met with the best response from pilots. In this set up, the pilot controls his ‘plan’ position using his left hand (the left hand already controls speed/ acceleration) and height rate is controlled on the longitudinal axis of the centre stick. This proved to be better than controlling all three axes on one hand, using a two-axis mini-stick top on the centre stick, which was found to increase pilot workload.

| By ensuring that the pitch and lateral/ directional blending regions were common, the number of control modes and hence blending regions were kept to a minimum. This helped to reduce the potential for pilot confusion during the transition...."