Category Archives: planes

On the back side of the power curve, and other oddities of the carrier approach.

Piggybacking on Spill’s post on the S-3, I should mention that he and I discussed Direct Lift Control quite a bit the other day.

DLC is used on several different aircraft. And while there are various ways of achieving the effect (the F-35C apparently programs the flaps) let’s take a look at the F-14 Tomcat’s version.

On a carrier approach, you have to balance several issues simultaneously. Airspeed, angle of attack and attitude, and lineup.

Lineup is the left or right displacement of the aircraft from the extended centerline of the landing area. Now, since the landing area of a carrier is canted to port 8-10 degrees, and the ship is moving forward, lineup is never static for the approaching aircraft. The landing area appears to be continuously crawling to the right. So a series of corrections for lineup have to be made throughout the approach. The amount of correction varies due to the variances in just how much ambient wind there is, and the actual speed of the carrier through the water.

Airspeed is critical as well. The lift generated by the wings of a plane is directly related to the speed of the plane, obviously. Similarly, attitude, that is, the amount of nose up pitch, and angle of attack, are critical with respect to the rate of descent. The two are related. AoA is very roughly the angle at which the wings are biting in the air. Obviously, attitude is related to this. But so is airspeed.

Changing any one of the three, airspeed, attitude, or angle of attack changes the other two factors. Given that precision needed for a successful carrier approach, that places an enormous workload on the aviator. And so, tools to reduce that workload are prized.

Here’s the other odd thing. You’d expect airspeed on an approach to be controlled by the throttle, and the angle of attack to be controlled by the control stick. In fact, it’s just the opposite.

When a carrier jet settles into the groove for its final approach, jet is supposed to be at a given airspeed (generally about 130 knots, but varying by type), and a specific angle of attack (again, varying by type) and at a specific rate of descent (again, varying by type, but aligning with the standard 3.5 degree glideslope used on a carrier approach). The jet would ideally maintain this slight nose up attitude all the way to touchdown. There’s no “flare” to stop the rate of descent just before touchdown.

When in this approach configuration, the jet is said to be on the back side of the power curve.  You normally think of jets, pull back on the stick, the nose goes up, and the plane climbs, right? On the back side of the power curve, the increase in induced drag from the increase in angle of attack actually causes the plane to slow down, and in fact, increase the rate of descent! Pushing the stick forward lowers the nose, increases the speed, and reduces the rate of descent.

In the cockpit of every carrier jet, there’s a quick visual aid to tell the pilot his angle of attack- the AoA indexer. What it is really telling the pilot is if he is fast or slow.  The pilot simply cannot glance down to his airspeed indicator. Even in HUD equipped aircraft, an AoA indexer is a faster way of imparting information to the pilot than a digital airspeed indication).

If you’re slow, pitch the nose down slightly. If you’re fast, pitch the nose up slightly. Helpfully, the “arrows” point the way you should go. If you’re seeing the green donut, you’re on speed. While the picture shows all three symbols illuminated, in operation, only one would show (or on some, two, for instance red and green, indicating slightly slow).

Having this tool to show his airspeed, the carrier aviator also needs information on his glideslope. As noted, there’s a notional 3.5 degree glideslope reaching from the ideal touchdown spot aft into space along the approach path. To give the pilot a visual reference, mounted on the port side of the carrier is “the meatball.” The IFOLS, or Improved Fresnel lens Optical Landing System shines a beam of light along that 3.5 degree slope. That beam is centered between datum lights that show the proper glide slope. If a pilot is high, the “ball” climbs above the datum lights. If the pilot is low, the ball sinks. Sink to far and the datum lights turn red, because landing short on a carrier approach means smacking into the aft end of the carrier.

When you hear Maverick at three quarters of a mile, call the ball, that’s what he’s seeing- confirming to the Landing Signal Officer that he in fact sees the IFOLS.

If our intrepid aviator is on speed, but a bit high, he would squeeze off just a touch of power. That increases the rate of descent. As he approaches the correct glideslope, he’d add on a bit of power. If our aviator is low, he would goose the throttles a bit, and then pull off a bit before climbing through the glideslope.

The problem is, it’s very rare to only have to make one correction. Instead, our aviator would end up having to jockey the throttle virtually to touchdown. All while trying to maintain the perfect speed, attitude, and angle of attack.

So back to DLC. If there is a way to suddenly increase or decrease the rate of descent, without having to jockey the throttles, that’s a boon. And that’s what DLC does.

On the F-14, on carrier approach, the spoilers were partially deployed. That inefficient use of the wing raised approach speed by about 10 knots. That’s the downside. On the plus side, if our aviator is high on his approach, simply using a thumbwheel on the control column allows him to add a bit more spoiler deployment. That instantaneously increases the rate of descent. Coming to the proper glideslope, releasing the thumbwheel puts the spoilers back in the default position, and instantaneously puts the Tomcat back to the normal rate of descent. The converse is also at work. Low? A little thumbwheel lowers the spoilers, increasing the efficiency of the wing, and decreasing the rate of descent.

Spill also mentioned the poor response time of the S-3’s engines at approach power. The lower the power a jet engine is producing, the lower its RPM. Inertia being what it is, it takes time for jet engines to spool up to produce more power.

For this reason, most carrier jets fly the approach with their speed brakes deployed. The higher drag means they need considerably more power to maintain their approach speed. That higher RPM also tends to improve throttle response times, as there is less inertia to overcome. If also means that if a pilot suddenly needs quite a bit more airspeed, all he has to do is pull in the speed brakes.

When Spill and I first talked about DLC, I was a bit surprised to learn one of the very first uses of it was on the Lockheed L-1011 TriStar jetliner. Apparently, it was rather highly thought of by the crews.

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The VAQ Squadrons

The fielding of the EA-6B Prowler tactical jammer aircraft in 1970 brought about some significant changes to doctrine and organization in carrier air wings. Previously, electronic warfare was something of an odd duck in the air wing. Typically at that time, an air wing would have two squadrons of fighters, two of light attack, a medium attack squadron, and an airborne early warning squadron. The wing would also host some detachments of odds and ends, such as a couple of A-3 variants as electronic warfare support and tanker, a helo detachment for plane guard and utility use, and maybe a couple of reconnaissance planes.

The sophisticated Prowler, combined with the Navy’s growing recognition of the value of both standoff and escort jamming in the face of the North Vietnamese air defenses, led the Navy to organize Prowlers in squadrons of four aircraft. Each Prowler seats a crew of four, and as a planning factor, a squadron generally has 1.5 crews per plane, or roughly 24 flight crew. Of the Prowler crew, only one is an aviator. The other three were Naval Flight Officers known as ECMOs or Electronic CounterMeasures Officers. The Prowler community was one of the first where the NFO community was arguably more important than the aviators. After all, anyone could drive the bus, but the skills of the ECMOs were quite specialized. At any rate, with only four planes, a Prowler squadron would have more aircrew than a light attack squadron with 12 planes. These Prowler squadrons would be designated Tactical Electronic Warfare Squadrons (or TACELRONS) with the designator VAQ. For instance, the Fleet Replacement Squadron is VAQ-129.

It took several years for the Prowler to fully enter the fleet. While deployed aboard a carrier, a Prowler squadron would report to the commander of that carrier’s air wing. When in home port, the squadron reported to the Commander, Medium Attack/Tactical Electronic Warfare Wing, Pacific Fleet (or COMMATVAQWINGPAC) at NAS Whidbey Island, WA, where all the Navy’s active Prowler squadrons were based.

As the 70s and 80s wore on, the size of Naval Aviation varied somewhat, and so to did the size of the Prowler fleet. The Reagan era build up saw an expansion in the number of air wings, and so to the number of Prowler squadrons.

Concurrently, the Air Force, seeing the same challenges in a future air defense environment, looked to leave behind its legacy fleet of EB-57 and EB-66 stand off jammers, and integrate a modern, supersonic escort jammer. And so in the early 1970s, began a program to modify some early production F-111A Aardvarks to carry a version of the Prowler’s ALQ-99 jammer system.

Entering into service in 1983, a total of 42 were delivered to the Air Force by 1985, serving in five different squadrons. Officially nicknamed the Raven, the EF-111A was almost universally known instead as the Spark ‘Vark. The Spark ‘Vark served admirably, particularly in Desert Storm, providing the same jamming support Naval Aviation had come to count upon.

But soon after Desert Storm, and with the collapse of the Soviet Union, and the subsequent so-called “peace dividend” drawdown, the Air Force made the decision to retire its F-111 fleet. And with that fleet gone, it was only a matter of time before supporting the EF-111A became prohibitively expensive.

Rather than spending the time and money to develop a replacement aircraft, the Air Force simply threw up its hands and said “we quit.” The Air Force simply forfeited what by now was known as the Electronic Attack mission.

But that didn’t mean the Air Force didn’t recognize the need for a dedicated Electronic Attack platform. Instead, it recognized that fielding its own platform was duplicative of costs. There was a perfectly good platform already in the Prowler. And in keeping with the Air Force ethos of central airpower management, the Air Force also didn’t see any reason why the Air Force should buy a platform already in service, duplicating the logistical tail involved.

Instead, the Air Force just decided the Navy would provide all its Electronic Attack assets in any future air campaign.

Now, the Navy didn’t really object to this. The only issues would be money for airframes and maintenance, and manpower to support such campaigns. After all, the Navy barely had enough Prowlers and crews to support its deploying carrier air wings. And there was no guarantee that a carrier air wing would be available to support any notional Air Force air campaign.

The Marines, operating their own Prowlers, quickly informed any and all that they were quite busy supporting Marine Air Wings and had no great desire to add any additional taskings, than you very much.

And so an odd hybrid series VAQ squadron was born. The Navy would buy extra Prowlers, and stand up the squadrons. The Air Force would not complain about Navy requests for funding for procurement and operations. Further, the Air Force would supply about half the personnel for the squadrons.

Known as Expeditionary squadrons, these VAQs would forego some of the training that traditional Navy VAQs went to, such as carrier qualification. Instead, these squadrons would be available to support taskings to a Combatant Command Air Component Commander.

With the retirement of the medium attack community COMMATVAQWINGPAC eventually evolved into Commander Electronic Attack Wing Pacific  or COMVAQWINGPAC (oddly, as there’s no counterpart on the Atlantic side.  COMVAQWINGPAC supports air wings in both the Atlantic and Pacific fleets, as well as all of what are now known as Joint Expeditionary Squadrons).

All the VAQ squadrons, both fleet and Joint Expeditionary, have either transitioned from the Prowler to the EA-18G Growler, or will shortly. In addition to the “schoolhouse” squadron, VAQ-129, VAQ-130 through VAQ-142 are currently stationed at NAS Whidbey. Additionally, VAQ-209, a Reserve squadron, is stationed at Whidbey. Three squadrons are currently Joint Expeditionary. Two new squadrons, VAQ-143 and VAQ-144 are expected to be established in the next couple years, and both with be Joint Expeditionary.

There’s one other interesting squadron at NAS Whidbey. Housing quite a few Air Force personnel at a Navy base is a tad unusual for those Airmen. There are quite a few things the Navy and the Air Force do differently. Where the rubber meets the road, most of the time, the integrated squadrons work well. But for certain personnel management issues, the Air Force needs its own on sight leadership. And so, to act as the parent command for Air Force personnel at Whidbey, the 390th Electronic Combat Squadron is stationed at NAS Whidbey. It’s not an operational squadron, and doesn’t own any planes. It serves instead as “ownership’’ of all the Air Force personnel.

 

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Greyhound!

If you were to ask a variety of naval aviators from the past half century what their favorite plane is, you’d likely get a range of responses from the A-4 Skyhawk and F-4 Phantom through the F-14 Tomcat and the F/A-18 Hornet. But if you ask a blueshirt on the 7th month of a nine month deployment, he might just tell you his favorite plane is the C-2A Greyhound Carrier Onboard Delivery (COD) plane. Why? Because that’s what delivers the mail!

Adapting the wings and engine of the E-2 Hawkeye to a new, roomy fuselage, the C-2 Greyhound was the first and only aircraft designed from the start for the COD mission. An initial batch of 17 produced in the 1960s were retired in the late 1980s. But the design was so sound that a second batch produced in the late 1980s soldiers on today, and will do so for at least another decade and a half. Carrying the mail is an important function, but only one of several for the Greyhound. Critical cargo such as spare parts, bringing passengers onboard, and ashore, and even supporting special operations are all in the mix.

Two squadrons operate the C-2, VRC-30 and VRC-40. Typically, each carrier air wing is supported by a two-plane detachment during its deployment.

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Oddball Aircraft

We’ll post a little later about one of the oddities of the EA-18G Growler squadrons, but in doing a touch of research, I was reminded of one of the more obscure aircraft in the Navy’s inventory right now, the MZ-3A.

“M” stands for multi-mission. The “Z” stands for lighter than air. Yes, the Navy operates a blimp.

File:Handlers prepare to launch the U.S. Navy MZ-3A manned airship for an orientation flight from Naval Air Station Patuxent River, Md., on Nov. 6, 2013 131106-N-PO203-532.jpg

Basically the Navy owns a commercial off the shelf blimp, and has used it primarily for various research programs. It’s been an on-and-off affair, threatened with cancellation several times.

The Navy actually has a long history of operating blimps (and that’s a story for another time), in addition to dirigibles. But as best as I can tell, this is the Navy’s first blimp since 1962.

Sadly, it’s a GOCO program. That is, the aircraft is government owned, but contractor operated. Which is a shame. It would have been very cool for some young officer to earn his blimp wing.

Yes, wing.

http://www.navlog.org/bag_pilot.jpg

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Early Apaches

How many times have we discussed the post-Vietnam era weapon acquisition of the “Big Five?” The M1 tank, M2/M3 Bradley, the MIM-104 Patriot missile system, the UH-60 Blackhawk transport helicopter, and the AH-64 Apache attack helicopter were all key components of the modernization of the Army after a generation of procurement lost to Vietnam.

We like to think of the Apache as being cutting edge technology. And to some extent it really still is. But we do have to acknowledge that it first flew in 1975.

This video touting the survivability of the Apache shows improvements to the weapons, countermeasures, and survivability of the Apache over its predecessor, the AH-1.

Sharp observers will note that the YAH-64 shown differed in a couple significant ways from today’s production model. The horizontal stabilizer used to be mounted at the top of the tail, but is now at the bottom. The profile of the nose has changed somewhat, as the YAH-64 didn’t have the complete TADS/PNVS installed. The sponsons along the nose are longer on the production model.

Production models also have far better Radar Homing and Warning devices and flare/chaff dispensers.

Still, the Apache is not invulnerable. But it was a great improvement over the limitations of the preceding AH-1 Cobra family of helicopters.

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Grumman at War

Spill mentioned today that with the retirement of the Prowler, the only Grumman aircraft on US decks now will be the E-2 Hawkeyes and C-2 Greyhounds. Mind  you, the E-2 will be around till at least 2045. But there was a time when the word “Grumman” was synonymous with carrier aviation.

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F-35C Sea Trials Extended Cut

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