Density altitude defined, effect on airtanker performance (part 2 of 3)

Low density air means high density altitude. An air tanker pilot friend, G, explains:

High density altitude is called that because the low density air found in hot air mimics the air found at HIGH altitudes. At HIGH altitudes and HIGH temperatures, there is not only less air for an engine to "breathe", but there is less air for the wings to ride on as well.

High density altitude is also known as performance altitude. High density altitude caused by high temperatures and high humidity can occur at lower elevations but is more of a problem at airports at higher elevations such as those in California and the southwest. If you are based at an airport at 3,000 feet above sea level and the air temperature is hot (e.g. 95 degrees) your performance altitude is going to be higher. The higher the density altitude the longer runway you will need to take off at a given gross weight. This can be computed and G explains how this works:

The entire exercise of computing density altitude is used to predict aircraft performance on hot days or in high places or both. All the airplane manufactures publish charts that help you determine how much runway you'll need at a particular gross weight and a particular altitude.  You add up the weights, figure the density altitude, (which tells you the altitude your airplane will act like its flying at), go to the performance charts and you find that at 8800 ft and full gross weight, your airplane needs, say, 6500 feet of runway to get airborne.  If the airport you are parked at only has 4000 feet of runway, you're hosed.  You either get rid of some weight, or wait until evening when the air cools.

What this means for air tanker pilots is that tankers working wildfires, e.g. in California or the southwest, may be forced to carry lower loads of retardant in order to compensate for higher density altitudes.

In my final article on density altitude, posting this Sunday, I will write a short piece on how density altitude affects helicopters.

Spartan C-27J

The Spartan C-27 (shown above flying in a 2007 airshow) was on display at the recent Paris Air Show (June 2009), see this video to see what this aircraft can do, with narration (that includes some technical details) in both English and French.

For more information on this aircraft you might want to read this short article.

This aircraft has generated some interest for its great possibilities in aerial firefighting. However, any uses in aerial firefighting probably won't happen anytime soon. As I understand it, the aircraft is currently being produced for military use only.

The military use of these planes may preclude their use for aerial fire fighting. Moreover, the current MAFFS units are designed only for the C-130 so modifications to either the MAFFS unit and/or the airframe would be required for the C-27.

Even if the C-27 was available for non-military use, the price tag of a new plane is too costly for aerial fire fighting budgets. Obviously, I am not in the position to know specifics, but using a 2007 Dept. of Defense contract as a guide, the cost comes in at about $25 million each. I used figures referenced of $2 billion over 5 years for 78 planes referenced here.

Nonetheless, the C-27 puts in an awesome performance in the video from the 2009 Paris Air Show, it is worth looking at.

And Speaking of SEATs

Take four minutes and go and check out this awesome video on Patrick's Aviation on SEATs working fires in France. Some of this is taken from the cockpit of a SEAT. You will see some footage of an AgCat shot from the SEAT cockpit. TL Stein tells me that the single-winged aircraft are an Ayers S-2R and confirmed that the bi-wing planes are AgCat G-164A's.

For a refresher on AgCats, see this earlier entry to my blog on AgCats. I wrote about the Ayer's Thrush aircraft here.

Reflections, S-2T's, SEATs and initial attack

I love the light tankers (S-2T’s and single-engine air tankers) in a special way. Perhaps it is because I live in NJ, and I have grown to appreciate and the role that single-engine air tankers (SEATs) have in initial attack (and extended attack). And it is not only NJ that uses SEATs, many states contract for SEATs. In the case of NJ, I am aware that the majority of our wildland fires are small in size. I also know that during our spring season that the NJ Forest Fire service deployed SEATs and helicopters to fires that were only a couple of acres in size. I am aware of this because of a couple of websites that I have followed, not because of the media.

Some of you know that I got interested in wildland fire fighting last July because I have a couple of friends who lived in or near the area burned by the Basin Complex Fires. And I have written about a couple of other larger California fires. I have written about CAL FIRE’s S-2T’s. Up until now, I have neglected to write about the very important role the S-2T’s, a light tanker, play in initial attack. Until now when I want to focus on initial attack.

California has an impressive number of large fires that make national news. I don’t know the numbers, but most of California’s fires are small in size, being 2, 5, or 10 acres. I have recently engaged in an e-mail exchange with an experienced air tanker pilot who will be flying S-2T’s this year. He was telling me about the importance of initial attack in keeping fires small and manageable until ground crews can get in:

Regarding the use of tankers, the best tactic is initial attack. In initial attack, S-2T tankers and helicopters are deployed to the wildfire as soon as possible in order to stop the spread and hold until ground troops have access and put it out. The goal is to keep the fire small: 2, 5, 10 acres maximum so it is ‘easy’ to manage. Roughly ninety-seven percent of fires in California are put out this way. The public may not hear about it. But...if you're not aggressive enough you get behind the power curve and then get complicated fast (wind, fuel, terrain...).

I understand that things can get complicated, especially with the drought, sundowners and the Santa Ana winds. And the terrain. I get that. Sometimes initial attack is not going to keep the fire small. But most of the times it does. How many houses have been saved, lives saved? You light tanker pilots -- the workhorses of CAL FIRE, other State fire fighting agencies, and the national fleet -- what you do is special. I want you to know that.

Evergreen 747

Evergreen International Aviation announced on March 24, 2009 (link no longer works) that its B747 supertanker received interim certification from the Interagency Air Tanker Board (IATB). IATB certification is required before an air tanker can be under federal contract. Bill Gabbert of Wildfire Today reported on the 747 receiving IATB approval here.

Capable of flying at 600 mph, the 747(tail number 979) can drop more than 20,000 gallons of retardant.

The 747 recently completed what is known as a drop test. Briefly, in a drop test an air tanker (or helitanker or helicopter with bucket) flys over a cup-and-grid matrix to test the coverage level for each type of drop.

Evergreen produced a seven minute video on the 747 supertanker:





Updated on August 3, 2015: I had to delete some old and outdated links from Evergreen Aviation that no longer work. At the time I wrote this article, they had a photogallery of the 747 and a page describing her capabilities. According to Bill Gabbert's May 2nd (2014) article on Fire Aviation it seems that Evergreen has declared bankruptcy.

DC-10 tanker: videos

For another good video, see this youtube video, and be sure to read the explanation of the video.

DC-10 Tankers: Tanker 910 history and specs

The first of the Very Large Airtankers (VLAT) put in service is tanker 910, first seeing service on a call when needed (CWN) contract with CAL FIRE in 2006 where it flew retardant drop missions on fires in southern California and one fire in Washington State. Tanker 910 is one of the DC-10 family of passenger jets. The first DC-10, designed and built by the Douglas Aircraft Company of Long Beach, CA, now the Long Beach Division of Boeing Commercial Airlines.

Starting in 2007, tanker 910 is under an exclusive use contract with CAL FIRE from June 15 through October 15.

Tanker 910 was modified and tested over four years by 10 Tanker Air Carrier with mostly private investment capital. Three external retardant tanks are mounted along the bottom center of the aircraft, capable of holding 12,000 gallons of retardant (50 tons!) capable of dropping a line of retardant in about eight seconds. Typical drop height is 500 ft. above ground level at about 170 mph. A crew of three -- pilot, co-pilot, and flight engineer -- flies the plane working with a lead plane when drops are made. They are not as maneuverable as CAL FIRE’s S-2T working on ridge tops or flat lands. But as they carry 12,000 gallons of retardant to the S-2T’s 1,200 gallons, one of the advantages of the DC-10 is that they can save the S-2T’s for initial attack.

See this page for more specs and technical information on the aircraft. CAL FIRE’s DC-10 tanker fact sheet (requires a pdf viewer) may be found here. Wikipedia’s article on tanker 910 may be found here.

10 Tanker Air Carrier now has a second DC-10 tanker, tanker 911 that was available earlier this year for fire fighting duty. It saw service in the recent Jesusita fire.

My next post: more pictures and video of the DC-10 tankers.

Very Large Airtankers

The last group of air tankers that I am writing about are known as the very large airtankers (VLAT). These are DC-10’s and 747’s. There are two DC-10’s (tanker 910 and tanker 911) and one 747 (tanker 947). All three saw service as commercial passenger jets before being modified for service as very large airtankers. The two DC-10 tankers can drop 12,000 gallons of retardant and tanker 947 can drop 20,500 gallons of retardant. I will be making one or two posts on each, starting with the DC-10 tankers.

copyright 2009 K. Tyler Miller

Martin Mars: US Forest Service contract and video tour

The Hawaii Mars will be under a new contract with the U.S. Forest Service this year, based at Lake Elsinore, California from June 1 through November 15, 2009. A Sikorski helicopter equipped with thermal imaging equipment will work with the Hawaii Mars filling the role of a “lead.” See this article by Bill Gabbert for more information. Bill also has a link to articles he wrote about the Martin Mars last summer when one of their tankers was based in northern California.

The Westcoaster, a newspaper based in Port Alberni, British Columbia has an article announcing the U.S. Forest Service Contract that may be found here.

For a 10 minute ride around the outside of the aircraft and a tour inside take a look at this video:

Martin Mars (part 1 of 2): history and specs

The Martin Mars, capable of landing on water, was developed for the U.S. Navy towards the end of the second World War as a transport aircraft. A total of six were built two were lost by 1950. The remaining four were retired by the U.S. Navy in 1959 and purchased by a Canadian Company known as Flying Tankers Inc. One crashed in 1961 and another was destroyed the next year in a typhoon. The remaining two, Hawaii Mars and Philippine Mars were converted for fire fighting in 1963 and are currently operated by the Coulson Group, based at Sproat Lake near Port Alberni, British Columbia.

A wikipedia article on the Martin Mars may be found here.

Each tanker is capable of carrying 7,200 gallons of water and has a 600 gallon foam tank. Finally are capable of delivering thermo-gel. Thermo-gel, also known as a water enhancer, does what its name implies. It enhances water’s suppression capabilities and is better able to coat fuels. If you are interested in reading more about water enhancers, see Fire Management Today, volume 67, issue 2. Starting on page 24, you will find a short article called: “The Latest on the evolution of chemical fire supression – water enhancers eyed for the future.” The authors include a text box with a brief description of foam, water enhancers, and retardants. The current issue of FMT along with archives of most back issues may be accessed on this USDA Forest Service webpage.

Refilling the water tanks involves “skimming” the water surface while maintaining a speed of 70 to 80 mph. Through the use of a scooping system water is injected into the tanks. It takes approximately 25 seconds to fill the water tanks. The video below shows this process:



For more information on the two Martin Mars aircraft, see this Coulson Group webpage. This page also includes a link to a specifications page.



A pilot, co-pilot and two flight engineers make up the crew of the Martin Mars.

Specifications:
Overall Length: 120 ft.
Height: 48 ft.
Wing Span: 200 ft. (61 m)
Gross Weight: 162,000 lbs. (73,483 kg)
Cruising Speed to Fire: 190 mph
Drop Speed: 138 mph
Landing Approach Speed: 115 mph
Touchdown Speed: 92 mph
Fuel Consumption (Cruise): 420 US gal
Fuel Consumption (Operations): 780 US gal
Operations Duration (normal): 5 1/2 hours
Area Covered, single drop: 3 to 4 acres
Drop Height: 150 to 200 ft.

Stay tuned for part 2 on the Martin Mars coming in a couple of days.

S-2T: end of season retardant tank maintenance

At the end of the season, or when maintenance on the retardant drop system is required during the season, the retardant tank is washed out. When this happens, the flapper valve and the tank doors at the bottom of the aircraft are in the open position. In addition the hotload cap is off. This allows any standing water to be vented from the system.

Here is a video of what this operation looks like:

S-2T: in action (2 of 2)

If you have nine minutes and want to see a good video of a few S-2T's in action along at a helicopter with a bucket working fires in California, take a look at this video. SCU refers to Santa Clara Unit.

S-2T: in action (1 of 2)

Here are a couple of very short videos of S-2T's in action. In the first video, the S-2T is working with a lead plane in the 2007 Zaca Fire in Los Padres National Forest. The first plane you see is the lead plane showing the S-2T where to make the drop. A few seconds later, the S-2T tanker flies through to make the drop.



In the second video, the S-2T tanker seems to be working with out a lead plane. At least a lead plane is not shown in the video. The last few letters in the name of this video is cut off, it is "CDF Air Tanker 78 Drops on Felter Fire/Santa Clara Unit"

martin mars

S-2T: making the retardant drop

When an air tanker such as an S-2T is deployed to a wildland fire, the air tanker pilot will be in touch with either the incident commander on the ground or some one known as the air tactical group supervisor (ATGS). The ATGS oversees aerial support for the fire, including retardant drops from a tactical aircraft, sometimes known as an air attack plane flying over the fire. The ATGS will be in touch with the incident commander (IC) on the ground. CAL FIRE’s tactical aircraft are known as OV-10’s and there is one OV-10 at each air attack base. The ATGS, after consulting with the IC, will give the S-2T tanker the information that s/he needs to make the drop, including but not limited to the location. In initial attack the S-2T pilot may make his own determination about the necessary settings and where to make the drop.

The settings that S-2T air tanker pilot (and other air tanker pilot’s) use for the retardant drops are on a panel on the cockpit. This is the same one pictured in the preceding post, so I will be using that picture as a reference. Perhaps you will want to open up a new window in your browser so you can look at TL Stein’s photograph and follow along.

The pilot adjusts the dial on the left to set the amount of retardant to be dropped while the dial on the right is set to determine the coverage level (also known as gpc). The coverage level is gallons of retardant per 100 square feet. Coverage levels are somewhat technical, depending on the type of vegetation on fire (fuels) and the fire behavior. The coverage settings dial is scaled from .5 to a maximum of 8 (gallons per 100 square feet). A switch known as the arm-disarm switch is set in the disarm position until it is near time to make the actual retardant drop. This prevents accidental drops. The button that the pilot pushes to make the drop, drop control switch (not pictured), is on the pilot’s control panel for ease of access. The door control (switch in the middle), is set to automatic.

Once the settings on the two dials are made, and the pilot is at or near the location and correct altitude for the drop -- 150 feet above ground level for the S2-T -- the pilot flips the arm-disarm switch to arm the system. The pilot has only to push the drop control switch at the appropriate time, the tank doors open and the drop is made. It is not merely the cockpit controls that make the retardant drop possible, there are various avionics (aviation electronics) and hydraulics that make the retardant drop possible.

If there is an emergency situation, the pilot can make an emergency retardant drop by pulling an emergency handle (not pictured).

Retardant at Ryan AAB and S-2's

In today’s post I am going to be writing about retardant mixing at Ryan Air Attack Base (AAB). This is possible because I have learned about retardant mixing operations at Ryan AAB from TL Stein. Moreover, Ryan has an S-2 air tanker. This provides me with a unique opportunity to link mixing retardant with a specific type of air tanker. In addition, unlike Ramona AAB which uses a mobile mixing system, Ryan AAB has a permanent mixing system. Ramona, the oldest AAB, uses a (mobile) mixing trailer because they have little room for expansion. Ryan like many other larger AAB’s use permanent mixing facilities.

Ryan Air Attack was first used as an air attack base by the USDA Forest Service in 1957 and the California Dept. of Forestry (CDF) started air attack operations at Ryan in 1959, making Ryan the first joint air attack base in the U.S. In the 1960s a permanent retardant mixing system was installed and shared by both the USDA Forest Service and the CDF (now known as CAL FIRE). In 1998 the USDA Forest Service moved their air attack base to the San Bernardino International Airport.

Thanks to TL Stein -- who made a short video on retardant mixing operations, took some photographs and gave me an excellent write up of retardant mixing at Ryan -- I am in a position to make this blog entry. The video is included in this post. After you watch this short video, I hope that you will have a good idea of how retardant mixing at Ryan works.



In addition to the video, I am including a couple of TL Stein’s photos. One is a photo of an eductor assembly at Ryan where the water and retardant pipes are labeled. As you will learn in the video, as water flows through the eductor, it creates suction in the retardant pipe. Retardant is therefore drawn into the eductor. The powdered retardant mixes with water at the point (see the photo) where the water and retardant pipes come together. From there it goes into a storage tank. The second picture is of the retardant mix control panel where the mixing operation and flow of mixed retardant to the various storage tanks on the base.

In my next post, I will write a little more about the process of loading the retardant mixture onto the S-2 and share some of TL Stein’s up close and personal photos of the S-2.

S-2T: history and specs

In the mid 1970’s CAL Fire’s fleet of air tankers were growing old and needed to be retired. These aging air tankers were replaced by newer Grumman S-2A aircraft (sometimes referred to as the S2-F1) beginning in 1975. These aircraft were used from the from the mid-1950s to the mid to late 1970s by the U.S. Navy for surveillance. The S-2A’s used by CAL FIRE were modified for use as civilian air tankers. The last of CAL FIRE’s S-2A air tankers was retired in 2005.

For a short history of the military service of the aircraft that is also known as the Grumman S2-F, the S-2 Tracker Museum has a webpage on it’s history. When you get to the home page, click on the “history” link at the top of the page.

By the mid-1990’s the fleet of S-2A’s had been in service for about 20 years, CAL FIRE began to prepare to retire the S-2A fleet. A decision was made to replace the S-2A’s with what CAL FIRE calls model S-2E/G series aircraft. Without getting into the complexities of changing model numbers over time, let’s just say that these were later variations of the Grumman S2-F aircraft. CAL FIRE acquired at least 23 S-2E/G aircraft from the Department of Defense. Marsh Aviation made extensive modifications to the S-2E/G aircraft including: adding a 1,200 gallon constant flow retardant tank, new turboprop engines, new avionics, and new electronics. CAL FIRE has 23 of these air tankers that they call S-2T’s. By 2005 the last three S-2T air tankers were delivered. Twenty-two are stationed around the state at CAL FIRE air attack bases and one is used for maintenance relief. CAL FIRE has a fact sheet on the S-2T air tanker that may be found here. The CAL FIRE Pilots Association has a nice map of CAL FIRE’s air attack bases that includes links for more information on each base, it may be found at this location.

Specifications of the S-2T:

length (ft): 65
wing span (ft): 73
turn radius (ft): 45
cruise speed (knots): 250
gross weight (lbs): 29,200
range loaded (st. miles): 1,500
contract operating weight (lbs): 29,200
retardant load (gallons): 1,200

C-130 MAFFS: retardant drop

The loadmaster, who sits at the loadmaster station on the MAFFS module in the cargo area in the back of the tanker works with the co-pilot in making the drop. You may recall from my earlier post, that the retardant flows through two discharge tubes that stick out the rear cargo doors of the aircraft. This means that cargo doors are left open and the load master wears a safety harness tethered to the rear of the plane. When it comes time to make the drop, the loadmaster monitors and then arms the system using the master control panel at the loadmaster station. It is the co-pilot, sitting in the cockpit, who pushes “the button” to drop the load.

The C-130 MAFFS works with what is known as a lead plane in making the drop. The lead plane flies as close as 1,000 feet in front of the tanker showing the path and height that the tanker will fly in making the drop. There is a nice article an the CAL FIRE MAFFS webpage about the role of lead planes in MAFFS missions. The article is called “exactly who is leading this mission”, it may be found here. Both civilian air tanker and military MAFFS pilots train with a lead plane every year.

To see a short you tube video on a C-130 MAFFS working with a lead plane go here.

C-130 MAFFS: activation

I believe that there are a total of four reserve/national guard bases, each with two C-130’s capable of being fitted with the MAFFS unit. This makes a total of eight C-130 MAFFS. One base is in North Carolina, and three are are out west. with California, Wyoming, and Colorado having one base each.

Before one or more C-130 MAFFS units are activated for wildfire fighting duty, the request has to go through a certain chain of command, so to speak. The incident commander in charge of a fire contacts his or her superior (department head) requesting type 1 air tankers (type 1 air tankers are the class of air tankers capable of dropping 3,000 gallons of retardant. The department head approves the request for type 1 air tankers and forwards the request to the state or regional forester. If the fire is on either privately owned land or State owned land than the request goes through the state forester. If, on the other hand, the fire is on land under federal control, then the request goes through the regional forester. The state or regional forester approves the request and passes it on to the National Interagency Fire Center (NIFC).

The NIFC is responsible for deciding what civilian contracted air tankers to send to the fire. If no civilian air tankers under national contract are available in the region the NIFC will look to see if any civilian air tankers under nationwide contract are available. If all are committed to fires or otherwise unavailable, the NIFC then goes through military channels to contact the U.S. Air Force to request C-130 MAFFS air tankers.

Once the request is approved at the appropriate military level, the closest reserve unit with MAFFS capabilities is order to mobilize and sent to the fire.

C-130 history

I was going through my C-130 data a few minutes ago and found a nice write-up on the history of the C-130 here.