F-35 Cancelled, then what ?

[LowObservable]

As a supersonic vertical lander the crowd should bow to it.

Or they may have their heads down to see where their fillings ended up.

[Bastardeux]

I had a friend in the old days who thought the same about retractable undercarriages.

How f@*king old are you!?

I don't really see an aircraft pioneering retractable undercarriage, as a valid comparison...

[SpazSinbad]

Yeah youse brits - be warned - and brung youse ear defenders with youse (to any F-35B display) and probably pocket your falsies (teef) also...

DOD PROGRAMS F-35 Joint Strike Fighter (JSF) [2013 end of]

http://www.dote.osd.mil/pub/reports/...2013f35jsf.pdf (0.5Mb)

"...F-35B Air-Ship Integration and Ship Suitability Testing...
...The Marine Corps has determined that new active noise reduction personal hearing protection is necessary for on-deck personnel because of the high level of engine noise. Noise damping materials and/or personal hearing protection may also be needed for below-deck personnel....

...F-35C Air-Ship Integration and Ship Suitability Testing
Although a number of air-ship integration issues are common to both CVN and L-class ships, such as lithium-ion battery storage, pilot flight equipment storage, need for new shipboard firefighting procedures, and high noise levels, some issues and their solutions are particular to aircraft carriers. The Navy has made progress in addressing some of these integration issues, but several challenges remain...."

...Engine noise is a potential risk to personnel on the flight deck and one level below the flight deck. The Navy has decided to procure active noise reduction personal hearing protection for on-deck personnel. Projected noise levels one level below the flight deck (03 level) will require at least single hearing protection. On most carriers this is a berthing area, but on CVN-78 this is a mission planning space; personnel wearing hearing protection in mission-planning areas will find it difficult to perform their duties. The Navy previously tested acoustic damping material in 2012 and is developing a model to optimize material placement....

[WildRover]

Bastardeux

I had a friend in the old days who thought the same about retractable undercarriages.
How f@*king old are you!?

I don't really see an aircraft pioneering retractable undercarriage, as a valid comparison...

Type in Google John Farley Aviation.......haha

Think he may know quiet a bit about the subject.

[glad rag]

Hmm, there seems to a lack of objectivity creeping into this [love] thread.

[gr4techie]

Jet noise comparison

Comparing the sound of aircraft in dB can be misleading, an difference of just a few dB can in reality be quite a lot. As dB is not a linear scale but logarithmic. The way I interpret it, for every 10dB the noise increase by a power of 10.
10dB=10
20dB=100
30dB=1000

As noise is considered, I reckon the Tornado GR4, with it's constant speed and variable noise is way up the league table. It amuses me when you compare the thrust of noisy "fast" jets with much quieter civvy airliners.

Anyway, I'm glad I won't be trying to sleep on an aircraft carrier with F-35's above me.

[Courtney Mil]

gr4techie raises a very important point here. The graphic showing how all the fast jets are "fairly consistant" in their noise levels is very misleading, using a log scale that few people understand to falsly make a point. For example, the 148 bd of an F-35 in burner is actually twice the volume of the 145 db in cold power - even though it looks virtually the same on the graph. Poor choice of illustration vithout a proper explanation.

[Fox3WheresMyBanana]

Au contraire, it is an excellent choice if you wish to play down a negative feature.

Mind you, it's also the standard measure in the industry. Perhaps people who don't understand logarithmic scales shouldn't be making decisions about information which uses them.

[SpazSinbad]

So via the chart an F-14B/D in A/B on the catapult at 153 db is somehow overlooked? I guess we will have to guess that the db for the F-35C on the catapult in burner is the same as the F-35A in A/B? 148 db? [changed - misread the 148 for 145 earlier]

Then some Hornets are at 2 db less or same (146-148) on the log scale? Wow Dem Tomcats sure must have howled at 153 db eh. No wonder a lot of USN people are deef even today wid dose Hornetoes on the go.
_______

I have read a few times now that USN LSOs often do not wear ear protection because they want to hear the engines on short final (in close - at the ramp). No wonder the LSOs do not like Hornets going to burner in the wires (not recommended by NATOPS anyway unless needed for whatever reason otherwise). Going to burner with the aircraft being arrested puts extra strain on all the bits and bobs.

[Engines]

Guys,

Perhaps I can help here, as I have some knowledge of the work done on F-35 noise issues.

Courtney and gr4techie are quite right to point out the issue of the logarithmic scale used for noise measurement. It's a complex area, and made more complex by the many scales used, not just 'dB', but also the more commonly used (and slightly more accurate) 'EpNdB', which is 'Ear perceived noise in Decibels'.

The real problem is not that the F-35 is significantly noisier than any 'legacy jets'. It's not. The key issue is that the programme's initiation coincided with the application of more stringent noise protection regulations in both Europe and the US. In a nutshell, the customers are no longer willing (or legally able) to tolerate the levels of noise exposure they happily accepted just a few years ago.

Because of this, the F-35 programme has done more work than any other in getting the best knowledge of the actual noise generated in all operational scenarios, including cat launches, VLs, and STOVL launches. Flight decks and ships pose a special challenge, because you can't keep personnel as far away from the noise source as on a land base.

Knowing the noise levels is also important in designing aircraft structures that are exposed to even higher levels of sound energy. Those of us who struggled with cracking Harrier heat shields and failing wiring know what 'acoustic damage' can entail.

The F-35 is as noisy as most other jets generating nearly 40,000 lbs of thrust from low bypass engines. There are some jets that are louder, and some quieter. The programme's predictions and measurements put in around the middle of the pack, but as I've explained, the incoming noise regulations led to a number of special programmes to assess all possible solutions.

Active noise reduction and more intrusive (in-ear) designs have made ear defenders better and better, but there are drawbacks, including problems in keeping the ear inserts clean and properly fitted. The next step could include larger helmets that reduce noise transmission through the skull - some of the designs were scarily similar to the 'Judge Dredd' model. Other solutions include reducing the noise exposure over time - at one stage, the CVF team were looking at 'acoustic shelters' around the flight deck to give crew some respite from the noise.

Bottom line is that managing noise exposure around high powered combat aircraft is a tough nut to crack. It's tougher on board. And the new regulations have made it harder still. But there are some extremely smart people working the issue.

Hope this helps

Best regards

Engines

[Courtney Mil]

Which shows even better how misleading your chart is Spaz. Those extra 5db you point out represent about 4.5 times the volume (power).

[Courtney Mil]

EpNdB is Effective Perceived Noise in Decibels. Due to noise saturation of the human ear it does not equate directly to hearing damage. Doubling the power ratio or sound pressure does not equate to doubling the perceived volume (EpNdB). Remember as well that this log 10 scale is all about ratios, not absolute sound pressure. Unless used relative to a reference, dB are somewhat meaningless.

But my main point is that the graphic on the previous page tends to suggest that all jet engines produce virtually the same noise. Clearly they do not and the spread of power across the audible frequency spectrum varies hugely.

[Engines]

Courtney,

As I alluded to in my last post, using straight 'dB' tells you how much sound pressure is being generated. But EpNdB is a better measure of the potential for damage to hearing. But Courtney's absolutely right that it doesn't equate directly to hearing damage. The duration of the noise exposure is, as I remember it, an equally critical factor.

As i said, it's complicated. Sorry, but there it is. As an example, during cat launches, the sound source interacts with the deck and the JBDs (and other aircraft if it's a two ship launch) (and other aircraft around on the flight deck) (and the wind) to create complex and variable EpNdB contours. STOVL launches present far less problems, but have still been worked in detail.

Not looking at the chart Spaz posted, but from my own knowledge of the predictions and tests that the programme carried out, the F-35 was not the noisiest aircraft the USN and LM found. It was certainly not the quietest. But, given the new regulations on hearing protection that were coming in, the programme took noise protection extremely seriously.

I know it's a lot more complicated than swapping dB (or EpNdB) numbers, but it's what the engineers had to do to find out exactly where the issues were and how they might mitigate them.

Best Regards as ever to all those doing the detail science type stuff (because it matters)

Engines

[SpazSinbad]

May we assume that the chart on previous page refers to full A/B for all aircraft? If so then this lil' tidbit may be one way that the horrendous noise of the Shornet and F-35C when catapulting is and will be mitigated?

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...BD_Testing.pdf (125Kb)

“...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 [Shornet & F-35C] 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....”

[GreenKnight121]

Originally Posted by SpazSinbad

So via the chart an F-14B/D in A/B on the catapult at 153 db is somehow overlooked?

As has been the listing for the non-afterburning EA-6B, which has been aboard USN carriers since the late 1960s, which matches the 148 Db of the F-35 in afterburner!

[SpazSinbad]

For those who do not want to read this long screed - just put your fingas in your ears as hard as you can and shout out loud "Lah Lah Lah Lah" - be a TeleTubby for the day. Others may read some text supporting the NRAC chart on previous page plus dis udda one....

Report on Jet Engine Noise Reduction April 2009 NRAC Naval Research Advisory Committee
Firstly from page 49:

"Appendix A - Terms of Reference - NRAC Tactical Jet Engine Noise Reduction Study
Objective
The noise on the flight decks of our carriers is 20 to 30 dB higher than any technology we have to protect the hearing of our Sailors and Marines. We are not in compliance with OSHA standards, and to quote the DASN for Safety, “We are creating a hearing loss certainty, not just a risk.” The noise problem cannot be solved by only hearing protection devices. The source of the noise must be reduced in addition to finding better ways to decrease the noise exposure times of our Sailors and Marines. The technology does not exist to achieve the needed decreases in engine noise from tactical aircraft jet engines without significant adverse impacts to performance. This study will investigate current technology for reducing tactical jet engine noise and will make recommendations for actions that can be taken to both reduce jet engine noise in existing engines and to be able to achieve lower noise levels in the next generation of tactical jet aircraft.

Background
Progress is being made in developing improved hearing protection devices to replace the current day cranial helmets that were designed in the 1950’s and are still in use on the flight deck. However, there has been no focused effort to reduce tactical aircraft jet engine noise. In fact noise has never been a design parameter for designing a new tactical aircraft, but rather aircraft such as the JSF/ F-35 have a contract specification to only mitigate the noise. No requirement exists for engine noise staying below any threshold noise level. The needed design tools to make such advances do not exist.

F-35A noise levels have undergone some measurement and appear to be comparable to the dB levels of other current tactical aircraft in Mil and afterburner. However, the noise power, watts per square meter, not just dB, generated by the F-35A is two times greater than that generated by the F/A-18 E/F. All tactical aircraft engines grow in thrust over time, and that equates to even greater noise in the future.

THEN... page 9.... "...Although it is desirable to have a single number to measure noise, near-field noise measurements require more than a single dB metric to fully quantify the acoustic pressure levels generated by an engine or to compare one engine to another.

Overall sound pressure levels, i.e., noise, are normally measured in dB, and are a summation of the sound pressure levels across a spectrum of frequencies. Because the human ear is not equally sensitive to all the frequencies of sound across the spectrum, noise levels at maximum human sensitivity between 2 and 4 kHz are factored more heavily into sound descriptions using a process called frequency weighting. Therefore, the noise levels affecting humans are normally shown in dBA (A-weighted decibels), a frequency weighted average.

There were concerns that the Joint Strike Fighter (JSF) F-135 engine would be noisier than existing engines and that hearing protection might possibly be inadequate for speech intelligibility for flight deck personnel. Accordingly, in 2002 the JSF Program Office funded a study of the noise environment during carrier qualification operations aboard USS John F. Kennedy (CV-67) and USS Abraham Lincoln (CVN-72) and during AV-8B operations aboard USS Nassau (LHA-4). This was the first time since a 1971 study that measurements of the noise during flight deck operations were recorded. Note that many of the conclusions and recommendations of reports generated in 1971 and 2002 are similar to those made in this report.

Noise levels approaching 150 dB are generated by today’s tactical aircraft. This chart represents a graphical representation of the peak jet noise levels (in dB) for several modern, high performance tactical jet aircraft. The noise numbers on the chart represent the maximum sound pressure levels (SPL) in dB measured for each aircraft in both Military and Afterburner (A/B) power settings along a 42 ft line parallel to the aircraft (representing the “foul line” on a modern aircraft carrier).

The data were collected by the Joint Strike Fighter Flight Systems IPT Vibroacoustics Team during the late 1990’s and are documented in the reports which are referenced in Appendix C. Additional data from a more recent (Oct 2008) test of the F-35 AA-1 Aircraft was provided by the JSF Program office as part of a brief to the NRAC Panel, and additional data from a test of the F/A-18E aircraft in 2000 was provided by the F/A-18 Program Office and is documented in a report titled “Effect of Jet Blast Deflector on Exhaust Noise of F-18E” also listed in Appendix C.

While the above data are considered the “best” data available, there are some concerns as to their absolute validity and the ability to compare data from one aircraft to another, because of the lack of standards for collecting such data as described previously.

Tests were a “one-off” event, and no attempt to produce repeatable data was documented. The Panel raises this concern because there have been two instances in which later measurements were made of both the F-35 and the F/A-18E/F, and differences of 4 dB and 2 dB, respectively, were measured. This shows that a single test, while an indicator of noise levels, cannot be construed as the true level. This variation could be caused by (at least) several contributing factors such as: test set up and execution, microphone placement, type, calibration, weather conditions, engine variability, etc.

NASA Glenn has estimated that at best a good consistent engine test may be able to yield +/- 1 dB for 1/3 octave spectra and +/- 0.5 dB for overall sound pressure levels with today’s techniques and technology. Flight test data will have larger error bars due to other influences such as aircraft position uncertainties and weather, which includes wind, humidity and temperature. Some, but not all, reports documented these variable conditions; however none of the data in the reports were corrected to a standard condition.

The selected test site can also induce variability, and not all aircraft were tested at the same location. This discussion is not meant to degrade the excellent work and effort done to collect the data which were provided to the NRAC, but it is a further justification for the Panel to believe that a set of standards for the measurement of near-field jet engine noise is required....
&
...page 13 ...Eliminating afterburner during takeoff will also provide a significant noise reduction benefit. Afterburners increase the jet noise levels by 5 to 10 dB above military power....
&
...page 25-26 ...Unfortunately, acoustic signatures have not been critical performance parameters in military tactical aircraft system development programs. For future aircraft programs, concern should be paid to acoustic signature effects on the hearing of our Sailors and Marines as well as the environmental affects on the local air base communities. The Navy must rethink how to incorporate lower noise signatures into a full system parameter requirement. This new contracting strategy will allow the prime contractor, in concert with the propulsion system contractor, to initially tradeoff the contributions of the various signature elements with the normal system performance elements (e.g., speed, range, and maneuver) and perform a system level optimization taking all elements into consideration. Without integrating all performance and signatures together, there can not be a system of systems optimization. In order to make significant reductions in aircraft noise, aircraft system contracts need to specify a noise requirement. This can be done by establishing noise as a Key Performance Parameter (KPP) and incentivizing the prime contractor and the propulsion system subcontractor to develop designs which meet this KPP.

In preparation for the next generation tactical aircraft, the Panel believes there should be a KPP for noise. The Navy should initiate a competitive design study to identify the technologies critical to minimizing mid-field and far-field noise for the next generation, high performance tactical aircraft. This design study should include the definition of the multidimensional vehicle design space available and the tradeoff factors between vehicle design characteristics and vehicle performance. In addition, the study should indentify the critical technologies, vehicle configuration and integration features to reduce jet noise and the realistic bounds of vehicle KPPs, including key mission performance and noise. Such a competitive design should be one of the steps in order to define a noise KPP for the next generation tactical aircraft...."
&
...Another chart from page 32 below....
&
...page 37 ...When noise levels exceed 85 dBA, for a period of greater than eight hours, humans run the risk of permanent hearing loss. Even with state-of-the-art protection providing 47 to 53 dBA of attenuation, one is still at risk in the high noise environments (145 – 150 dB) around jet aircraft. The magnitude and impact of noise transmitted via bone and other media such as fluid is largely unknown. The ear canal, if maximally protected, will reduce the noise by 47 – 53 dB. As the sound intensity increases past 110 dB, noise can be transmitted to the hearing apparatus via other routes – most notably bone conduction. In high noise environments noise is transmitted by bone, so attenuating the noise only in the ear canal will never be sufficient at noise levels above 150 dB. The Navy must anticipate that some fraction of the “at-risk” population of Sailors and Marines could lose their hearing, even when outfitted with protection that occludes 100% of the noise. Navy medical research into antioxidant therapy for brief impact noise in Marine subjects, suggests that there may be an effective “pre-exposure” therapy available that will increase noise-level tolerance. Data also suggests that post exposure therapies can potentially re-grow damaged hair cells. This kind of research needs to be expanded to include chronic noise exposure on the flight deck.

Noise levels below 500 Hz are normally not recorded by either dosimeters or medical audiograms. Although in the research environment audiograms routinely record down to 125 Hz. Various anecdotal reports have noted both the presence and absence of subjective discomfort attributed to “low-frequency” noise. Those who have stood near an F-22 or F-35 at high power levels report uncomfortable sensations and believe their internal organs are moving, such as could be caused by low frequency noise. Other occupational environments — undersea sound and human physical vibration — have produced human injury and disease. Critical organs of the body have harmonic resonances ranging from a few Hz to 400 Hz. For these reasons, greater bio-medical research into the adverse effects of low frequency, air-propagated, sound is needed. As is the case with our hearing conservation research recommendations, we recommend that this research be guided by individual, job-specific, noise level exposure data....
&
...page 39-40 ...Since 2003, the Navy has invested approximately $15 million in tactical jet noise reduction research. This research has focused primarily on university basic research and subscale/lab demonstrations. One full-scale demonstration was conducted to assess several technologies, and did lead to the current chevron rapid technology transition effort for introducing chevrons into the F/A-18 E/F F414 engines.

The Air Force investments in engine noise have been solely focused on measurement and modeling, largely for community noise which has been and remains the focus for the Air Force. [b]The JSF Program has invested in numerous acoustic surveys of baseline noise data for the F-135 engine and also the F-35A aircraft. However, these efforts were focused on characterizing the noise level for hearing protection, and providing adequate hearing protection for the aircrew and maintenance personnel – a requirement of the JSF contract.

The JSF Joint Program Office initiated a study (by Pratt & Whitney, General Electric Aviation, and National Aerospace Laboratory – funded by the Netherlands) to investigate reducing the F-35 near-field personnel noise and far-field community noise. This study was a low-detail, high-level assessment of noise impacts. It evaluated and estimated the effectiveness and viability of currently available and emerging “public domain” technologies for reducing the propulsion system’s contribution to the F-35 acoustic footprint...."

[Hempy]

So, how much would it cost to research and implement noise reduction measures in military jet engines versus say researching better earmuffs?

Russians? Pencil?

[SpazSinbad]

F135 Exceeds Expectations During Live Fire Survivability Testing

F135 Exceeds Expectations During Live Fire Survivability Testing 20 May 2014 ASDnews

F135 Exceeds Expectations During Live Fire Survivability Testing

"...Three F135 test series were conducted, including Short Takeoff and Vertical Landing (STOVL) propulsion system tests; dynamic and static engine ballistic tests; and finally, total fuel ingestion tests. These tests were aimed at better understanding the advanced engine control system, the capabilities of the main engine with battle damage, and to assess the engine's fuel ingestion tolerance.

According to the JASPO report, the "STOVL propulsion system was very tolerant of damage with little performance loss over the course of the testing." The report also indicated that the "propulsion control system is very capable in its ability to withstand and accommodate damage via built in redundancies… [and] the engine showed a high tolerance of ingested fuel."

The JASPO report concluded that damage to blades and vanes in both the lift fan and main engine did not result in catastrophic damage, and that, in fact, the F135 engine and its control system are capable of withstanding and accommodating damage, and providing information to alert the pilot to the damage sustained by the system. The data collected from these LFTs will be used to update assumptions used in the F135 vulnerability assessment.

"This series of tests on the CTOL/CV and STOVL variants is intended to mimic battlefield damage in wartime scenarios...."

[Lonewolf_50]

Noise, California, and Environmental Impact Statements.

Over a decade ago, I was in a working group that had as one of its objectives the forwarding to the flags/stars recommendations on bases for operating the FRS/RAG when JSF was deployed.
This was a joint deal, not a Navy deal, so I think USAF RTU was their term. (Gawd, those meetings sucked.)

At the time, our little group (one of many in various places dealing with such matters) was hung up on the noise problem the JSF presented.

Some of the local pissing and moaning around NAS Lemoore regarding their resentment of the sound of freedom as delivered by the Super Hornets was expected to get worse, since part of our brief was that Super Hornets were a few dB less noisy than a JSF.

This 2009 study puts a number on something we had no power to change, but had to account for in our staff recommendation. Thanks for the post.

However, the noise power, watts per square meter, not just dB, generated by the F-35A is two times greater than that generated by the F/A-18 E/F. All tactical aircraft engines grow in thrust over time, and that equates to even greater noise in the future.

Blah. The greenie twits in California will be up in arms over F-35's making noise in the San Joaquin Valley.

Again.

[SpazSinbad]

NAS Lemoore is preferred West Coast home for F-35C jets 15 May 2014 Sentinel Staff

NAS Lemoore is preferred West Coast home for F-35C jets

"Naval Air Station Lemoore has been named the preferred West Coast home base for the F-35C aircraft, according to a final environmental impact statement...

...A final decision will follow a mandatory 30-day waiting period, after which the assistant secretary of the Navy or his representative will sign a record of decision to be published in the Federal Register."

The Final EIS is available for review at: Environmental Impact Statement - Home

EIS DOCUMENTS for NAS Lemoore: Environmental Impact Statement - Document