The DOT&E report on the Initial Operational Test & Evaluation (IOT&E) trials of the Marine’s Amphibious Combat Vehicle (ACV) illustrates a concern related to the trend towards wheeled vehicles instead of tracked and that is the age old automobile plague of flat tires. Many followers of armored vehicles have speculated about the performance and, therefore, advisability of substituting wheels for tracks with the obvious concerns of traction, durability, vulnerability, etc. being raised. Now, we have the IOT&E results to offer some actual data.
ACV land mobility in the desert environment was often degraded by tire failures, which led to 2-hour mission delays while crews replaced or swapped tires. The ACV platoon did not have a hydraulic jack or other means to lift the ACV without an LVSR Wrecker. Some tire failures could be attributed to incorrect tire pressure settings in the Central Tire Inflation System (CTIS) on the ACV. As crews actively monitored CTIS settings, tire failures were less frequent. (1)
So, to no great surprise, we see that wheeled vehicles are subject to flat tires. The DOT&E report notes two main issues:
1. Modified driving may be required. DOT&E notes that ACV drivers will have to learn to modify their driving to avoid obstacles that may penetrate tires and cause flats. According to Gunnery Sgt. Christopher Sorrell:
“Since IOT&E, we’ve had the ability to change tires out more expediently, and since we’ve also learned how to ultimately not pop or puncture more tires, based off of terrain, and actually making smarter decisions as drivers of what we should and cannot maneuver over,” he added. “And comparable to an AAV, it’s the same. We can maneuver over anything that an AAV can maneuver – no changes in that – but it is like, hey, am I really going to roll over a bed of nails. In an AAV, I could, but maybe I’m not going to do that in an ACV.” (2)
So, the solution to flat tires is to learn what the vehicle can and cannot drive over? Hmm …
On the face of it, that seems like a reasonable suggestion/solution and a simple matter of training. However, a bit more thought reveals a lot wrong with that. While avoidance of suspect obstacles may be easily achieved in a staged test under ideal conditions, what happens when the driver/vehicle is confronted with darkness, fog, rain, confusion, and the stress of combat where avoidance of certain types of terrain or obstacles is not the highest priority? How will the driver detect and avoid suspect obstacles then? For that matter what happens if the only immediately desirable direction happens to lead through suspect terrain or obstacles? Does the driver abort the mission due to a ‘bed of nails’? Is that really all it will take for an enemy to stop an ACV movement or assault … just scatter some nails?
Other than a mine, tracks don’t care what they travel over. By using wheels, we’ll be giving up some mobility and operational capability. We’ll have combat vehicles with obvious and common limitations. Is this really combat-desirable?
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| Wheeled ACV |
2. Tire replacement is problematic. From the USNI News website,
The [DOT&E] report suggested the Marines think about “adding a spare tire kit at the section level” and find a better way to change the vehicle’s tires.
Sorrell described the tire issues as a learning experience for the Marines, who used trial and error to figure out what worked best in the field. For example, during testing, the Marines would dig a hole in the ground to change a tire because at the time they did not have tools like a jack.
“But now we have the capability, since IOT&E, to basically bring an air compressor to the field with us, be able to lift a strut up in the air underneath the tire, and change a tire out in less than 30 minutes,” Sorrell said. (2)
Doesn’t having a fast, easy method for changing tires on a wheeled combat vehicle seem like something someone in the program should have thought of long ago? But, I digress …
Is driving over a stick or obstacle the only way to get a flat tire? What about shrapnel and small arms fire? Is that all it will take to stop an ACV … just shoot out a tire? I’m not terribly knowledgeable about wheeled vehicle combat operations but is a single flat tire really enough to mission kill a vehicle and require immediate changing as seemed to be the case in the IOT&E trials? If so, that would seem to be a poor design for a combat vehicle potentially subject to large amounts of shrapnel and small arms fire.
On a closely related note, the ACV size and weight present some recovery challenges.
The weight, height, and size of the ACV made recovery of a disabled ACV challenging and time consuming, at times requiring additional LVSR support. When vehicles sustained severe damage to suspension components or became mired, one or more LVSRs were required to recover the ACV. LVSRs are on the Table of Organization for the Assault Amphibian Battalion, and Marine Corps Maintenance Battalions. Additional LVSRs may be required to support future ACV platoon or company-level operations. (1)
Summary
I find myself deeply troubled by the US military’s push toward wheeled vehicles. I don’t follow the issue closely enough so I don’t know whether it’s been carefully studied or not but my vague impression from reading bits of discussion over the years is that this is another example of an assumption based on no tests and no experience. Common sense would suggest that tracks are far superior in terms of ruggedness and performance. There may be financial arguments for wheeled vehicles but, as we’ve often stated, combat assets should never be designed to business cases. Combat vehicles should be designed for maximum combat performance and all other factors assume a secondary importance.
I’ll continue to follow this with great interest. As I say, I’m not a combat vehicle expert.
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(1)Director, Operational Test & Evalution, “FY2020 Annual Report”, Jan 2021, p. 121-123
(2)USNI News website, “Marines Defend ACV Development as Program Matures”, Mallory Shelbourne, 19-Feb-2021,
https://news.usni.org/2021/02/18/marines-defend-acv-development-as-program-matures
Coming up on 40 years for the LAV-25 and I haven't been hearing this complaint about it my entire life. I really want 2 basic heavy chassis for all the high end combat vehicles. One with tracks and one with tires. Module gear the rest including when it is and isn't amphibious. Plan the design for our logistics structure or plan our future logistics for it. Although, personally designing it our existing logistics makes the most sense as it needs to then go out and use the rest of the world's road in some capacity.
ReplyDelete"Is that all it will take to stop an ACV … just shoot out a tire? I’m not terribly knowledgeable about wheeled vehicle combat operations but is a single flat tire really enough to mission kill a vehicle and require immediate changing as seemed to be the case in the IOT&E trials?"
ReplyDeleteUS Army Strykers roll with run-flat tires. Pretty much every operator of wheeled fighting vehicles that I can think of uses run-flat tires, precisely so that even if all 8 wheels are flat, you can still drive and keep moving.
It's worth noting that the ST Engineering Terrex, the other competitor for the ACV program (which was also an off-the shelf solution with an existing production line) has run-flat tires.
"run-flat tires"
DeleteI would have assumed that to be the case but, if so, why was DOT&E testing discussing the issue as if it was fatal? Why wouldn't testing just push on with a flat tire if that's what would happen in combat?
The larger issue is the modifications and limitations imposed by wheeled vehicles if you now have to avoid certain terrain, as noted in the DOT&E report. That seems unacceptable.
While run flat tires allow a vehicle to continue traveling after the tires have been burst, they don't last forever. The vehicle can only travel so far and move so fast before tires finally give out under that 11 ton weight - enough to exit a fight after dropping off the infantry squad, enough to continue along for a while in combat, but not long enough for a prolonged test program, hence the need to change tires.
Delete"Common sense would suggest that tracks are far superior in terms of ruggedness and performance."
Not necessarily. The old M113 was infamous for how easily it threw a track, leading to the risk of rollover. Quoting Federation of American Scientists:
"The vehicle is not mission capable if any one track shoe is damaged. If the M113 loses a track, breaks a track shoe or the vehicle throws a track, extreme caution must be exercised in maintaining control. The driver must immediately release the accelerator and let the vehicle coast to a stop. Applying braking action, i.e. brake pedal, laterals, pivot or any type of steering controls causes the vehicle to pull to the active or good track and could result in a roll-over."
(https://fas.org/man/dod-101/sys/land/m113.htm)
Tracks getting thrown, linkages broken, these are a bitch and a half to change in the field, because they're so heavy, and that's before you have the problem of mud getting into the works and drying up and gumming up tracks and your drive wheels. Every tanker you ask will talk your ear off the pain and suffering of track changing. Conversely, wheels are much easier to change out in the field. A trained crew can change a tire on a Terrex in 15 minutes, a full set in 2 hours. That's still faster than changing out an entire track length, which can take hours just to do for one side. If your track comes as sets of track shoes on a pallet, it'll take even longer because now you have to connect those track shoes into track lengths. And if your track is thrown under the tank or all tangled in the suspension, you're not moving anywhere, you're stuck until the recovery vehicle arrives.
There are pros and cons. Tracks are hardier against shrapnel and obstacles, but your top speed is much lower than wheels, and if the track is thrown, then getting the vehicle moving again is a very time consuming affair. Wheels are more vulnerable to damage, but it's easier and faster to change out a damaged wheel than it is to replace track length - you've got 8 individual wheels, vs 2 loops of track.
The mobility argument for wheels is that 8x8 all wheel drive, high wheelbase and oversized tires allow wheeled vics a credible offroad capability; not quite to the same level of tracks, but viable enough that they're not limited to road systems, and on flat terrain, wheels allow a higher maximum and cruising speed vs tanks.
On the other hand, tracks let you carry more armor - there's only so much weight wheeled suspension will take before it fails.
It's all about tradeoffs.
Nice summary!
Delete"Tracks getting thrown, linkages broken, these are a bitch and a half to change in the field, because they're so heavy, and that's before you have the problem of mud getting into the works and drying up and gumming up tracks and your drive wheels. Every tanker you ask will talk your ear off the pain and suffering of track changing."
DeleteAh, yes. A hundred times yes.
There's a reason everyone involved with such vehicles HATES it when tracks start bitching, and it's a good one.
Yes, tracks are sturdier, go pretty much everywhere and definitely have their uses, but there's reasons for going with wheels besides financial arguments.
Personally I'd still go with tracks in this particular case, mind you, but I could be persuaded otherwise.
@Ghiskey Wolf
DeleteNice post
I would think after what two decades we would have some good data out of Iraq and Afghanistan given the deployment of the Strykers, The Bradley and I assume the Marine AAVP and the LAV... It seems like somebody should be able crunch data on reliability and vulnerability of each approach in light APC or whatever (non tank) vehicle. Not to mention the same potential data from everyone else who sent similar vehicles.
There are reasons why some vehicles should be tracked, and some wheeled.
DeleteBut bean-counters want a single solution to every problem, and then bitch when they wind up with shitty vehicles because someone insisted on their pet solution to the problem.
"There are reasons why some vehicles should be tracked, and some wheeled.
DeleteBut bean-counters want a single solution to every problem, and then bitch when they wind up with shitty vehicles because someone insisted on their pet solution to the problem."
The other problem with single solutions is that they lead to single suppliers and over time that leads to lack of competition and that leads to higher prices.
I thought DARPA was working on a system that could change from tire to track vehicle in a few minutes to allow ground troops to support a myriad of terrain and not be worried about flats or other issues. The video I saw back in the day had it seemed like this was the way to go, but cant speak for costs or issues.
ReplyDeleteThey also have that concept where you put a track mechanism on a wheel axle to improve a wheeled vehicles performance when needed. It would be good to know if this was changing a tire so the flat tire can be repaired or something else. Why burn cash like that in training or validation, just so long as run flat works when they are still shooting at you.
DeleteThe Russians had tanks and armored cars that could run on either wheels or tracks back in the 1930s, nearly 100 years ago. It didn't catch on.
DeleteContinuous track has its own problem. It breaks while just move in rough terrains. This is part of reasons while possible, tanks are put on other vehicles (train, etc.) than on their own.
ReplyDeleteToday, armies in nations also put wheeled fighting vehicles together with tanks. Wheeled vehicles are lighter and faster, suitable for hit and run (thanks to artillery radars, today, artillery also perform hit and run).
Current AAV7 is pretty outdated (very slow on water). Years ago, Marine's AAVV project ended in failure. Marine needs a replacement.
Even China, with its famous type 05 amphibious fighting vehicle (on water speed near 3 times of AAV7) found it has weakness - amour not strong enough (if increase amour, then, speed suffer). While don't know China's solution, I think that Marine does need a vehicle is fast to conduct hit and run. Add amour is also not a solution for Marine for obvious reasons.
German's Boxer is a stellar wheeled amour vehicle.
ReplyDeleteChina's ZBL-08 and ZBL-09 (all wheeled) family are also excellent.
While Chinese marine's type 05 amphibious fighting vehicle (or ZBD-05) is continuous tracked with a ~3 time speed of AAV7 over sea. They are not fast enough on land in comparison with wheeled vehicles.
Boxer is a great big target that dwarfs most other vehicles including MBTs - a turreted Boxer is 3.24 metres tall (compare to 2.44 metres for M1 and 2.98 metres for a M2 Bradley). Given it's light armour I suspect it would have a very short lifespan on an actual battlefield.
Delete"While Chinese marine's type 05 amphibious fighting vehicle (or ZBD-05) is continuous tracked with a ~3 time speed of AAV7 over sea. They are not fast enough on land in comparison with wheeled vehicles."
DeleteOne thing that the ZBD-05 family includes is an amphibious tank that can fire relatively large shells on its way to the beach. I can't imagine it to be very accurate firing from the surf, but it probably makes a pretty useful intimidation and fire suppression weapon.
A couple of rounds from an amphibious tank is not fire suppression. THIS is fire suppression! : LSM(R) - Fire Support Ship
DeleteThe photos of tanks firing from the water is probably just a PR stunt. For one thing, a tank has only a very limited supply of rounds and using them up in a blind fire suppression attempt before you get to shore is not what anyone would do.
Agree we need a modern LSMR, or enlarge it to a Land Attack frigate. But firepower anywhere you can get it is firepower.
DeleteQuoting from your thread, “Chinese Type 05 Amphibious Assault Family,” dated 9 Aug 2019, “This gives China an initial assault wave, heavy firepower vehicle that is very similar in concept to the US WWII LVT(A)-4 amphibious tank. The US found this type of vehicle to be absolutely essential for amphibious assaults and I see no reason why the requirement has changed today. In fact, given the absence of naval gun support, an initial wave heavy firepower vehicle is even more essential.”
An initial amphibious heavy fire support vehicle is absolutely essential … but not in an offshore suppression role!
DeleteWWII style amphibious landing is no longer viable, except against weak enemies.
DeleteToday, amphibious assaults need first control air and sea, several rounds of air attack will then take out enemies' heavy weapons on land. followed by helicopter landing, at same time, navy will conduct mine sweep to clear a passage, then navy engineer to build a simple dock so large ships can dock and unload heavy equipment.
Marine should focus on amphibious assault under Navy's command. However, today, Marine seems want to become second Army.
Now I'm confused. According to Wikipedia, the original phase 1.1 requirements for this vehicle called for a vehicle that could "drive with a wheel blown off". If it can do that, I'm not sure why a flat tire is such a problem. Perhaps the weakness is not as great in actual combat as the testing suggests.
ReplyDeleteTracked armored vehicles are operationally superior in most ways. Period.
ReplyDeleteLutefisk
"Doesn’t having a fast, easy method for changing tires . . ."
ReplyDeletePer the USNI report, they can change out a tire in thirty minutes, which should improve over time. But, the overall downtime depends on how quickly they can get a spare tire.
But, as the Marine Corps Times reported "the biggest worry to come from the report was how cramped the troop carrier portion of the vehicle was, making it difficult for 16 Marines in a fully loaded ACV to quickly escape in an emergency."
Given that the Marines lost an AAV last July, not getting out quickly in the case of an emergency is most troubling. Maybe that means carrying a few less troops or rearranging the seating, I don't know.
The ASLAV operating in northern Australian grasslands lose wheels to tree stumps. They are followed by fitters who repair on the spot.
ReplyDeleteIn interesting amphibious news Australia has issued a RFT for a LARC-V replacement. All existing LARC-V were made in the 1960s. They are still used by US and Australia military and some tourism operators. See https://adbr.com.au/commonwealth-progresses-army-amphibious-capabilities/
I have wondered if screw based locomotion might be useful in amphibious vehicles. There was research and some prototype vehicles manufactured in the USA and USSR in the 1960's. Fordson tractor made a tractor with a screw drive in the 1920's. The major down side with a screw drive is the very low speed on hard ground. They do quite well in water and soft ground.
ReplyDeleteA vehicle that had both a screw drive for the aquatic transport and either tracks or wheels the surface transport might work.
A transporter with a screw drive that can carry a M1A1 tank or other vehicles over the surf and soft ground and deposit it on hard ground further inland would open up many potential points of assault that are not considered feasible with tracked or wheeled vehicles.
Some video of vehicles with screw drives.
Chrysler Marsh Amphibian
Fordson Snow-Motor
The Drive article about screw based drive
"The major down side with a screw drive is the very low speed on hard ground." Obvious problem: Hard ground constitutes the VAST MAJORITY of places where our ground forces will fight. Screw drives might not even be useful for amphibious warfare, if there are reefs near the coast. I doubt it's cost-effective for the USMC to invest in such a niche capability.
DeletePropellers and water jets are completely ineffective on hard ground, yet amphibious vehicles have been outfitted with both. I don't see screw propulsion as a replacement for tracks or tires, rather as a replacement for propellers and water jets. An added benefit of the screw drive is it may function as a type of skirt armor to protect the tracks or tires from flank attacks.
DeleteIf the screws were placed on moveable mounts that could place the screws directly below the vehicle or at the sides of the vehicle, the best mode of transport could be selected for the given soil or sea conditions.
The real benefit for the screw drive is on the water, properly sized to provide for the complete buoyant lift for the vehicle, the screw drive keeps the rest of the vehicle out of the water, limiting the overall water borne drag of the vehicle. Water transit speeds should be much faster than current amphibious vehicles.
As a carrier vehicle sized for an MBT, you've described the LCAC but with a propulsion system that handles less types of terrain and is significantly slower. LCAC will go over shallow reefs, up rocky beaches, over a few trenches, and across a parking lot in the time it takes a screw drive to cut through the reef. The one problem with big LCACs is they're big and expensive and we can't risk them in the first waves.
DeleteAs an auxillary propulsion system on an AAV, I like the concept of the moving mounting, but the reality is the whole system would be very heavy and likely have worse performance in the water than a typical prop/jet, and the wheels/tracks make any advantage in sand redundant. Any gains in sailing speed from raising the hull are lost to the inefficiency and weight of the screw, not to mention how wide and long the base would have to be to achieve stability with an AAV hull elevated fully out of the water - due to the size alone you couldn't even take half as many of these with you compared to conventional AAVs!
Ultimately LCACs dropping non-amphibious units on the beach gives you the best capability, and we need to build a bunch of moderately protected LCACs and associated Amphibs to fill out our amphibious fleet.
Mike Sparks created an entire website devoted to warning about the inherent weakness of the Stryker (the Army's wheeled vehicle).
ReplyDeleteThink of it as the "navy-matters website for the Army". ha ha ha
combatreform.org
Continuous track is easy to break. It is a common problem for tanks. Go to web and you can find armies all over the world encounter this problem on their tanks.
ReplyDeleteThere are many tradeoffs between performance in water and performance on land. I would think you need at least two vehicles--one a truly amphibious vehicle where those tradeoffs are resolved in favor of performance in water and the other, which may or may not be amphibious, where the tradeoffs are resolved in favor of performance on land. The latter might be delivered ashore by Mike boat or LCU or LCAC.
ReplyDeleteThere's a couple of things we need to further take into account for the tracks vs wheels debate for the ACV. Firstly, cross-country mobility. Yes, wheels will never achieve the same level of cross-country mobility in rough terrain as do tracks. However, this needs to be looked at in a holistic manner. Where and why are tracked IFVs employed? In support of tanks. The IFVs thus have tracks to keep up with the tanks they're supporting.
ReplyDelete...The USMC no longer has tanks.
Another consideration with terrain: outside of mangrove swamps, which no vehicle can get through, tracks or no tracks, the kind of terrain you get at beaches is generally adequate for wheeled vehicles. I can take my Hilux to the beach (well, it IS a Hilux...) This ties in to a further point, which is "what's your CONOPS? What are you trying to do with ACV?" Is it a battle taxi to drop off troops on the beach, or bring them a dozen miles inland to establish defenses/assault enemy defenses? Or is it supposed to range two hundred miles inland with an infantry squad? (to do what?) That's something that only HQMC can answer, however.
So, yes, cross-country mobility is great, but what I'm getting at is does the USMC require that sort of cross country mobility? Can an MEU even use that sort of cross-country mobility effectively? I'll argue that is the USMC straying away from their purpose into being America's second land Army, trying to do on a shoestring things that the Army is better-equipped and better able to do.
So, unlike a fair number of commentators above, I don't consider wheels to be a disadvantage or a dealbreaker.
There's another thing to consider and that's what happens if you get a flat tire. Yes, tires are more vulnerable to damage than tracks. Yes, tracks can probably soak up machinegunfire better than tires can. But the enemy isn't stupid: if they're shooting at a tank, they'll be using RPGs (and ATGMs if they have them, not everyone is the US Army which issues Javelin as a SQUAD-level weapon). Tracks are not proof against RPGs - an RPG hit has a good chance of detracking a tank. Consider the Abrams TUSK and Bradley BUSK armor kits, which add side ERA plates to cover the hull and offer some protection to the tracks and road wheels. If your tank or your IFV is detracked, you're stuck in place. There's no way you can move without calling in a recovery vehicle. There's no way to do a field repair of the tracks, it will take too fucking long. Can a tank crew change out their tracks, sure, but it's a whole day job for a single crew, it's a slow, labor intensive process, and it's done at base in a safe environment.
Meanwhile, with wheels, sure, machinegun fire will burst the tires. But if you've got a flat, you can quickly drive away on the other 7 tires, find cover, swap the wheel in 15-30 minutes - or just get the hell out of there. With run-flat tires, even if all of your tires are flat, you are still mobile enough that you can crawl back to base on your own power - you don't need a recovery vehicle to rescue you.
Nice comment. I especially like the part about CONOPS.
DeleteActually I wish to point out that recent wheeled vehicles trend is a trade off. While wheeled vehicles have significant drawbacks off road, they performed superiority in roads, allowing them to self deploy on long distances. Which is why so many armies want them.
ReplyDelete"While wheeled vehicles have significant drawbacks off road, they performed superiority in roads"
DeleteGiven that most combat occurs 'off road', what does that tell you about the desirability of wheels versus tracks?
On the other hand, unlike tanks and bradleys, they don't need tank transporters to carry them over roads.
DeleteIt's trading a certain measure of tactical off-road mobility in order to have better strategic self-deployment mobility. It really depends on where you're going and what you're doing, which goes back to the CONOPS.
As an example, there's Japan's Maneuver Combat Vehicle, a wheeled tank destroyer. The thinking behind the MCV is that because it's using road wheels, the JGSDF can rapidy deploy the lighter MCVs using the highways and airlift, using them to plug gaps and stall invasion forces while waiting for the tanks to arrive. You can use them to reinforce islands with ro-ro ferries, there's a lot less logisitical effort than with moving tanks. That's the Japanese CONOPS.
So like I said before, it really depends on what the USMC CONOPS is.